I believe that most Americans agreed with majority of Trump's policies such as his stance against China, NATO and his toughness with illegal immigration.
The problem with Trump was always his persona and his mannerism.
His egocentric and narcissistic behavior made him the president in the first place, however, his insistence to act like a complete moron and his failure to be even remotely presidential cost him his downfall. One can only take so much of that bullshit before saying enough is enough.
I know several diehard Trump supporters who would openly admit that he is a jerk and an asshole, but to them, his policies were enough to keep him in the office.
In the end, he alienated too many people with his theatrics, constant non-sense, tweets and rudeness. Amazing that he just couldn't see the signs coming, specially when most of his closest allies threw in the towel and quit his administration. The writings were all on the wall for him.
In my opinion, the president of the US represents much more than policies. He needs to project leadership, be tough when needs to be, but also be a good politician who understands that not all battles can be won with sword. That was never Trump. He ultimately didn't have what it takes to be a President. The lack of moral character and empathy, his narcissism and his love for praise and loyalty are all shared traits with most third-world countries dictators. Americans experimented with him for one term and most realized their mistake.