I think power and money corrupts people. Plenty of people who started out as honest business people turn into monsters. As you move up the ladder, less and less people are honest with you. Some are climbing the ladder because they are unhappy and that definitely makes things worse, they think money or power will make them feel better, when actually I’ve found living with less and doing things yourself is ultimately more satisfying.
Anecdotally, I personally felt how wealth corrupted me - when my economy car was totaled and my insurance rental gave me a Mercedes because they were out of reasonable models . After a week of driving it I started feeling like I was better than other people on the road. Luckily I got a replacement crappy hatchback and became a normal person again.
It’s pretty quick. Insects come back in about two years, although it can be a little weird- you may get massive population growth of bugs you aren’t thrilled about ( we had a year of millions of earwigs first)
then predators (one year was baby lizard mania )
Bumblebees really took off about 3 years in. Birds too.