“WHY? Why do they hate him so intensely?”
First, because they believe he is completely unqualified to have power over them. He’s like the characters Rodney Dangerfield played in “Back to School” and “Caddy Shack”, a rich but uncouth guy who accidentally comes to have power over the country club or college where he clearly does not belong. He sticks out like a sore thumb, he’s “not our kind”, and it drives a lot of people crazy. The presidency and the power it represents is “sacred” to those who worship power (even though they mostly see themselves as atheists), and Trump defiles that sacred thing. Sort of like a porn-star somehow getting elected Pope.
Second, because most people operate on the superstitious belief that he President controls and is responsible for what happens (even when he doesn’t really control something, like the way a virus behaves). If you think things are going well, you love the President as if he had given you the good things that you see happening. If you think there are massive problems and things are going over a cliff, then you hate the guy who you see as destroying your world. We, who support the President, see things as going pretty well and just needing some improvements, which we hope/expect our guy will provide. If you see yourself living in a country that never was all that great and rapidly getting worse, you fear/expect that this President-from-hell will make the damage so much worse by his incompetence and his evil nature.
...a rich but uncouth guy who accidentally comes to have power over the country club or college where he clearly does not belong.
That covers after he got elected. It doesn't explain the hate fest from the time he announced his candidacy.
I'm not even going to bother with your other comment as it also only comes into effect after he is elected.
There is a root issue here, I just can't grasp what it is.
The most plausible thing I've heard yet.
He hadn't even won the primary though. See what I mean?
Got to get to the root.