Voters deeply anxious over the economy and a candidate who doesn't primarily attack her opponent on such pochef book issues, despite being tremendously vulnerable on that front despite banking his entire campaign on being a "populist reformer".
Gee, I can't imagine what could go wrong.
Dems more or less allowed Trump to corner the anti-establishment populist sentiment. Granted he had a relatively easy time of it given the sheer extent of establishment support Clinton had, but to not even issue a direct challenge to his triangulation was a grave mistake.
"Anti-estblishment" is much harder a case to make when being attacked for rightly hang the same economic positions as Romney and W., right down to active use of outsourcing.