Re: Why did McMahon bury Vader?
If you watch that Cornette vid, it was pretty much covered the reasons why he never done as well in the WWF as well as he should have. The main one being that he got off to a bad start by refusing to change his name to the 'Mastodon' which would have meant that the company would have made more money from his merchandise if they pushed him. After his recent return to Raw, Vader admitted himself that he should have went with McMahon's suggestion and kept the Vader name for his work in Japan (he had already burned his bridges with WCW).
His WCW past: Was definately something that attracted the WWF, but remember Kevin Nash never rose above midcard status in WCW and enjoyed a huge push shortly after joining the WWF. Not being their creation was not as much a factor as not being able to repackage the character and make as much money as possible from him.
His stiffness: Pissed off the one guy that you didn't want to piss off at the time. However, if there is money to be made then the WWF could have easily worked around that. After all, they pushed other guys with a similar reputation like RVD & Benoit. McMahon once said that his favourite wrestler on the roster was Fit Finlay (around 2005/6). Being stiff is not a problem as long as you bring other things to the table as guys like that have their uses in any wrestling company.
Shawn Michaels: See all of the above. HBK knew Vader's card was marked already and could be as much of a prick he wanted with him. As Cornette said, Leon White is actually quite a sensitive guy so the likes of Hogan & Michaels could run rings around him in regards to politics.