Trump played as an outsider. And media, his own party and everyone treated him as pariah or an outsider. This just confirmed Trump's credibility in eyes of voters looking for outsiders. I'd say that's a large part of why he won.
More than a second actually. If you read both my comments, I think we agree.
The Democrats managed to persuade themselves that the public would elect the most "establishment" candidate imaginable. This after their own anti-establishment candidate had done incredibly well in the primaries (and had been polling above Trump). Books will be written about this self-delusion.
EDIT: Sorry, hard to detect sarcasm.