Doesn't Understand Promotions

I was a department managwer for over a year (that ended last week) and I don't understand the managers I had AT ALL! Can someone explain some things to me? Was it just this company? Am I wrong? If I am... feel free to tell me.

How can a manager skip over all the "been there a long time, knows it all, and is bored with their current position" and promote a person to an assistant store manager who ONLY knows customer service, and had NO clue about the sales floor or receving????

Or how does a manager move someone to another store and promote them to a department manager the day after they stand at customer service and swear at their immediate supervise because they were asked to run register?

Or how do you write someone up for something and then admit that they know it wasn't even your fault?

Or yell at someone for not doing something that they were in the middle of doing???

Was I wrong to quit? i'm jobless and broke but I feel a lot better. My health was really suffering. I think all of these things are wrong. Does that mean I wont be a good manager????