In my experience, some (and I would emphasise some) people in positions of authority think they’re invincible. I know of one former head of a government department who ensured that promotions and upgrades went to followers and sycophants to the detriment of others. No money changed hands of course but it’s an abuse of power that equates to corruption in my world.
Not all examples of poor management are examples of corruption. If the head of an organisation thinks that having underlings who display loyalty, obey without question and never present unwelome alternatative viewpoints is the best thing for the organisation, and makes promotion decisions on that basis, that may be a poor decision that will have negative consquences, but it's not corrupt.
Similarly if the head thinks that men are generally better workers than women and so favours men over women in promotion decisions (or the other way around) that may be a poor decision, and illegal, but it's also not not corrupt.
Corruption is the abuse of power, office, authority etc that has been entrusted to you for public benefit, or for the benefit of your employer, your church, your club, your society, etc to secure private benefit (for yourself or for someone else).
If what you do is intended to benefit the organisation that you lead or serve, no matter how wrong-headed your thinking is and how unlikely it is that any benefit will result what you do is not corrupt. But if what you do is intended to benefit you, or your friend, or your relative rather than the organisation that you lead or serve, it is corrupt.