He bad mouthed the boss (well his staff did) publicly.
In any line of work, if you insult your boss, you can expect to be fired.
The IG investigation was tied to "did he break the UCMJ" type of issues.
Since he wasn't quoted as saying anything negative, he was cleared of wrong doing.
While at the same time, his staff was insulting the President; therefore the President fired him.
So, what I guess he did wrong was he didn't stop his staff for making personal comments about our national leadership.
Agreed. You can't do what he (his staff) did. We beat that to death a few months ago. That being said, it sill gave me a a chuckle when I read it.