1.
At first, Mayor Mayor refused to have anything to do with her new job. They couldn't make her do it if she didn't want to. Well, she did give Solid Wall permission to hire some workers to starting cleaning up around town hall, giving away the socks for free and clearing out all the debris, but that hardly counted. Solid Wall had asked her and it wasn't like that it mattered whether or not she allowed him, since he probably would've just done it anyways. It definitely didn't matter that people commented that this was good 'delegation of responsibility,' because she didn't have any responsibilities, because she didn't accept that she was the mayor.
She didn't care that everyone who'd lived in the era of Pilgrim Heart was now a little afraid of her. She certainly didn't care about the little bribes they kept trying to give her in order to placate her. She only took the lavish apartment the Riches furnished her with because it was better than the gazebo, and she only attended the delicious and filling dinners the Apple family regularly invited her to because it would be severely rude to ignore their invitations. It wasn't that she was enjoying the newfound wealth that political power gave her. It was just accepting proper hospitality from others.
The dinners that the Apples put on for her were many and good, and she was always invited to sit at the head of the table, where Granny Smith usually sat. Granny Smith would glare at her throughout the entire meal, while her daughter and son-in-law nervously explained how grateful they were that taxes remained low in Ponyville, and what an honor it was to have her to dinner with them. She didn't really like them, but did enjoy the company of the young colt that was currently their only child, although it was clear that there was another one on the way. He didn't speak much, but he would smile and look down whenever she talked to him about books. Once he'd let slip that he liked the Little Mare on the Prairie books, and then looked death stricken before clamping up into silence one again.
He called her Mayor Mare, respectfully, which was a much better name then Mayor Mayor Mayor, and Mayor Mayor used her much expanded paycheck to send the child a brand new set of the Little Mare on the Prairie books as a gift. It was not long after that regular dinners ended. Perhaps Granny Smith's curiosity about the mare was sated, or perhaps her daughter and son-in-law were adequately reassured that she was a good pony and wouldn't tax their business to death.
Once the socks were cleared and town hall was in something resembling a state of repair, Mayor Mayor asked Solid Wall to have the annex taken down. It was only a request of course, not an order from a mayor, but it was nice to see things getting done. She also started signing legislation in, because otherwise it didn't get enacted and nothing got done. It was only a temporary thing though. She was most definitely not a mayor, and she most definitely didn't enjoy being a mayor.
2.
It was several years later that Mayor Mayor came to the horrible, life-shattering realization that she enjoyed being mayor. It happened one afternoon in her office, when she was signing legislation because she had nothing better to do. She'd just finished signing her name to a new budget when it occurred to her that she could abuse her power, like Wintergreen had. She could play with some numbers and fish out room in the budget and she could finally build a new library.
A good library.
A much better library then Ponyville had ever had. The type of library that would rival Manehattan Central Library. The kind of library that might one day even rival Canterlot Royal Library. Something to really put Ponyville on the map. With the power of her mayoralty, she could finally make her dream come true. She could become the head librarian of a magnificent library. It was only possible because she was the mayor. She couldn't have done it as librarian, she wouldn't have had a chance, but with the power and money that came with her horrible unwanted job, she could make everything she dreamed of happen. It was awful. She loved it.
(She even, in her most horrible, secret moments, knew that she liked making speeches and cutting ribbons. It was always a thrill to see some new part of the poor and broken town expand under her leadership.)
It didn't take her long to draft the orders, the only thing that she needed was an idea. Something to make a truly unique and amazing library. She looked out the gaping chasm in town hall that once was a wall with a window. There she saw an ancient oak tree, it's branches hanging just above the squat skyline of Ponyville.
There was her idea. There was her library, there was her magnum opus, the thing that would make her remembered throughout all the future generations of Ponyville. It wouldn't just be a library, either, it would be her home, and she would have all the books she ever wanted, all the books she could ever ask for. Just as Wintergreen could have as many socks as she wanted. Of course, Mayor Mayor would be more reasonable in her demands. Obviously, she would never ask more than was possible for any pony to get done on their own. She was a benevolent mayor.
"How in the name of Celestia am I going to turn a tree into a library?" Solid Wall asked himself, staring at the old oak. He was flummoxed.
3.
In the end, most historians agreed Mayor Mayor was the worst mayor in the history of Ponyville. It was largely agreed that her early success in expanding the town was largely thanks to Mayor Strawpony's policies, in particular his 'free socks for everypony' policy, which was his last act in office. The massive influx of cotton was sold off at a large profit on the open market by Filthy Rich, and the taxes from those sales were what largely spurred the urban renewal process that launched Ponyville into notoriety.
When neighsayers pointed out that Strawpony was not in fact a pony at all, and therefore describing his administration as having policies at all was absurd, the historians balked. Just because Strawpony was a scarecrow didn't mean his contributions meant nothing. To be ignorant of the contributions of other species other then ponies to greater society was to discount much of important history, and the historians wouldn't stand for that kind of nonsense.
The real reason Mayor Mayor was considered the worst mayor in ponyville's history was because of the sheer amount of disasters that occurred during her administration. The town was attacked, destroyed, turned into the chaos capital of the world, and many other horrible things before she was through. Of course, none of these things were Mayor Mayor's fault, and she dealt with all of them with level-headedness and a degree of competence, which was all anyone could really ask for. The truth was that this was the real job of any mayor. Not cutting ribbons, or making speeches, or signing legislation or disciplining junior staff or anything like that. The real job of any mayor was to take the blame when things went wrong, and Mayor Mayor excelled at this above all else. She truly was the best worst mayor ponyville ever had.
Of course, by the time the new library was finished, it really didn't matter what history would say about Mayor Mayor. She was happy, she was surrounded by the books that she loved in a large library with an endless selection. The bedroom on the second level was decorated just to her liking and she reveled in it. Everything was wonderful. She was a head librarian at last. Once there was room in the budget, she would expand the library even further by expanding the basement, and then she would have junior librarians to order around. Soon, Ponyville library would be the envy of all the libraries in Equestria- No! The world!
Less than a year after the Ponyville Library was completed, Mayor Mayor was kicked out to make room for Celestia's prized student, who took it as her permanent residence. She also took the title of head librarian, and she even brought with her a junior librarian, a little dragon, who she could order around to her heart's content. The library, which Mayor Mayor had built as a labor of love, would forever be associated by future generations with Twilight Sparkle, who'd had nothing to do with its construction.
Sometimes, you're just fated to lose, no matter what.