You've acknowledged Trump was not your first choice during the 2016 primary...and based on the voting/polling he was the first choice of only 1/3 of the people that ended up voting for him in the general election. Why did the 2/3 of Republicans that didn't want Trump in the primary end up picking him in the general election? Pretty simple, to vote AGAINST Clinton.
That's where Dems are now. It is no different. Put me in the any living, breathing person category if that person is running against Trump.
Ironically, if your first choice (Kasich) was the nominee, we would have voted for the same person in 2016 as I also thought Clinton was a bad choice.