I don't particularly think his supporters matter, as they are mostly sheep and not one of the main facisim roots.
It's the fact that more than half of America's entire media apparatus is entirely behind Trump.
They dominate airwaves and have entire control over several local information ecosystems allowing them to brainwash entire populations with wall-to-wall propaganda that is completely aligned in its message of refuting and obfuscation of reality.
Regardless if the people are racist, scared, simple minded, trained to blindly accept specific authority or whatever, is mostly irrelevant in a society with journalistic integrity, and a non-corporate/private interest owned media.
It's no surprise that some people believe outrageous, impossible, contradictory, claims when every reality authority available to you exclusively tells you coordinated lies.