Anyone that expects this will only last four years hasn't been paying attention on history books.
Keeping it impersonal (and only understanding/analyzing "how" the elections were won/lost), I think that "Trump didn't win". Instead "Democrats lost", took a risky bet and to quote the meme "the risk I took was calculated, but man, am I bad at math". [0]
[0]: https://i0.kym-cdn.com/photos/images/original/000/963/073/e2...
EDIT: I think it was Bill Burr that said on his (latest) SNL monologue "you would think that after the assassination attempt they would just give it to him" (because yes, that was a critical security failure, and so badly designed (the "security" of the event") that one could easily be tricked into thinking that it was purposeful)(a proper Hanlon's razor)