We should remember that, even though Hillary lost the election narrowly, Trump literally blasted the Republicans in the primaries out of the water.
Generally speaking, a great many people are sick and tired of the same ol'/same ol' Washington establishment as they feel it has let them down over the last several decades, which is why Donald and Bernie did so well, even though Bernie couldn't gather enough of the minority vote to put him over Hillary.
Even though Trump is still popular with his base, he's still catering to the Washington establishment, and this might get really "old" after a few months and years because I don't really expect any breakthrough economically, especially since trickle-down economics has been proven to be only marginally effective, while at the same time ramping up the deficit.
If Elizabeth Warren decides to run in 2020, she could be that person who, like Trump and Sanders, could capture the attention of these Americans who are "fed up and we're not going to take it any more!!!".