I really don't get it.
Well into 2016, even most Republicans dismissed him as a joke, as they had in previous years when he ran or considered it. Then many started hopping aboard the bandwagon when they saw he had a chance, so they might as well take advantage and use him in that way. Sure, he had a hardcore base, but then so did Reagan and later Clinton, (although Clinton was more groupies).
But how it became so cultish is beyond me. I never liked Reagan or Clinton either, but I could see that both they had a certain charm that appealed to those that liked them.
I don't see that with Trump. I just see the same wannabe celebrity that folks took rather unseriously here (to put it nicely) since the 1970s.