They steal from those they have the power to steal from. Power is measured as a delta from a baseline. If corruption requires power, it requires inequality.
There's is poor people who exploit other poor people. Poor people that sends children to work for example. Only the rich can use power for evil? A stronger or armed person has a power differential with a weaker person. A smarter person has more power than a dumber one. And it's impossible for the smarter one to lend intelligence to another, and to the stronger one to give muscles to the weaker one. And in spite of this, many humans behave compassionately and respect laws.
If as you say, corruption requires inequality, and there are inequalities that cannot be leveled, like strength and intelligence, and power, then monetary equality won't stop corruption.
In a hierarchical organization like a government there will be different power levels.
So, there are inequalities you cannot level. And you suggest that reducing wealth inequality will make the world better. I don't know, I still believe that aiming at reducing poverty is a better goal.
Why? Because without poverty people won't suffer because of survival needs. And without inequality you don't guarantee that there's no poverty.
To me, only a very envious person would put equality over reducing poverty.