Corruption came back, but in the meantime, a lot of operation efficiency was lost.
Swapping out a police department is much like swapping out a dev team - you are losing a LOT of tribal knowledge, and you have few guarantees that the new dev team won't make their own, potentially different, mistakes. They also lack experience in the domain.
How? Is Minneapolis also disbanding it's entire civil beaurcracy? Is Minneapolis also blacklisting the current police from other jobs? Are they letting the current police take home any equipment they currently have access to?
Your Ukraine comparison is slightly better, but "corruption came back" doesn't address whether the move was beneficial or not. Nobody expects the result of disbanding the police to be a perfect racism free police force.
The removal of one public official is nothing like the deBaath party decision. Acting like there is a possibility this situation mirrors Iraq is ridiculous.