Unions outside of the US are also full of corruption, at least the 3 that I have information from my family members. One of them was the union representative in their branch, and after a few years left the union altogether after seeing what goes on and that none of the organizers actually care about doing something. In general members extracted extra vacation days that were given to do union work and that's it.

Unions are just like political parties after a while, the people that get involved in them have a particular personality, and pretty much none of them think you should take pride in the quality of your work, it's generally people who are very sour and see only enemies in their work life. Otherwise they'd be doing the work and getting rewarded for it.