There’s this curious thing in mathematics where most things are either obviously true or obviously false and those that aren’t are mostly inconsequential. Those that remain are certainly more interesting but also typically their proofs are a few obvious steps.

Obvious in this case means something like “clear to a mathematician familiar with the field” or “otherwise many things will fall apart”

This leads to the situation where if a mistake is found in a theorem then it is likely still true even if the proof is wrong.