When the Crystal Heart shone, it was the last straw. A certain something reached its breaking point. However, that was far from the beginning.
The conditions had been lying there for some time, waiting for a large enough signal.
When Discord escaped his stone prison, the immense chaotic power he threw around so casually ate away certain borders; the Elements of Harmony did what they could, but there were things lodged in certain places. And yet, the event's start was still far in the past.
It was a disaster millennia in the making.
When Luna fell and Nightmare Moon rose, the sheer hate she felt, and the evil magic tainting her, attracted the attention of the inhabitants of a less connected realm. And it still isn't far enough.
When Discord ruled the land the sheer insanity he spread, the creatures he twisted, and the misery he caused - it all set a precedent, a familiarity. And he should have known, but he often ignored the advantages of sanity.
The draconequus should have remembered that like chases after like.