Corrupt mods? Maybe every once in a while something actually corrupt happens but dude. As istara stated it's an immense amount of work to be a default of main sub or of any large sub. My roommate is a mod of r/music and they have to get through things fast or else all the modmail and other things will completely bog them down. Especially if they have other subs. Just look at the mods to subscribers ratio, it's going to be a very, very small number and then factor in that these people are volunteers. People overreact to the modding on Reddit way too much.
Corruption does not necessarily imply a conspiracy. Corruption can occur from simple mismanagement. There are incidents of mod-corruption on reddit, as you admit, but the heart of matter is that many people are sick of wallowing through the garbage on reddit to find quality discourse.