Perhaps it was. Point is, we have NO CLUE what it was yet everyone gives their opinion anyway.
I think it was probably something internal as he SUDDENLY couldn't care less about a job that he previously loved, and suited him down to the ground.
Bloom has pretty much said as much, that Gus's mind was made up in March (or even earlier) to leave. Can you not remember the u-turn in his attitude? We were 4th in the league, and he suddenly couldn't care less. He loved this job previously, but something happened behind the scenes that meant...