Discord has become worse than bad.
Worse than evil.
He became an idiot.
When Pinkie Pie and Rainbow Dash make a 'stupid cupcake' which makes the consumer an idiot for a day, they decide to give it to Discord, just for a laugh.
But the effect does not wear off.
Discord is dumb for life.
It's a fun, quick laugh. At times that is all you need. You may pour yourself into seriousness, yet there is no harm in quick comedy. Keep it up.
This is the saddest tale I have ever read
4677554 How is it sad?
Mad
https://www.fimfiction.net/story/11307/pinkamena-4-recovery. Not done by me. Read and weep.