How do people get permanently suspended?

Hi, I want to know more on how people get permanently suspended because my account recently got suspended. I'm not sure what I did wrong but checking my match history, I did not afk or get reported(if i'm reported, a small window would open telling you to agree that you will never do it again right?). I will admit that I have afked before and I got timed before I could enter match making queue but thats really about it. I am certain that there are other ways of getting permanently suspended but i'm pretty sure that I didn't do anything wrong. Please, anyone tell me why I was suspended.

Thanks.