Also did he consider the consequence if he hadn't messed it up? Maybe you get one Excelsior team up like STVI, but he's not going to show up in every film. Leaving the enterprise would have meant his career would have tanked even earlier.
Plus he was also mad at a little boy in STIV who was meant to be a distant relative of his, but kept messing the line until they ran out of time and the scene was cut.
Funny how it's always someone else's fault.