> If the managers are not taking bribes or favors for better treatment that isn't corruption
You have a very narrow definition of corruption here. A manager using his management powers to intentionally make his life easier at the cost of the company is corrupt regardless how he does that. He could do that via bribes, but also could do things like hire a lot of deadweight people to bloat his org and raise his own salary without making the company more productive, that is also corruption since he hurt the company to benefit himself.
That isn't "bad management" since it was done intentionally, he knew what he did was bad for the company and good for himself. Corrupt management often masquerades as bad management to avoid getting sued, but it is still corruption.
You have a very narrow definition of corruption here. A manager using his management powers to intentionally make his life easier at the cost of the company is corrupt regardless how he does that. He could do that via bribes, but also could do things like hire a lot of deadweight people to bloat his org and raise his own salary without making the company more productive, that is also corruption since he hurt the company to benefit himself.
That isn't "bad management" since it was done intentionally, he knew what he did was bad for the company and good for himself. Corrupt management often masquerades as bad management to avoid getting sued, but it is still corruption.