I feel like the founders felt that the voting base would not possibly be dumb enough to support an individual like Trump. They put in appropriate guardrails but never thought such a large portion of the country would push so hard towards fascism.
Of course they didn't. They wrote all this assuming that wealthy white landowning men would continue to be the only ones who could vote. Populism was not something on their radar.
And to that end, they specified that Presidential Electors should be appointed by state legislatures. They didn't go so far as to prohibit choosing them by popular vote (because they left it up to the legislatures to decide), but having the People choose the President is clearly not what they had in mind. What they were actually going for was something more similar to the way parliamentary systems choose the Prime Minister (by vote of the parliament itself). The only difference is that they wanted the state legislatures to choose instead of Congress, for added Federalism. (That's also why Electors are a thing, by the way: they couldn't have 1 vote per state legislator because different states had legislatures of different sizes and they needed to make it fair between states, so instead they had each state legislature choose a number of Electors equal to that state's representation in Congress.)
Same with Senators, too: those were supposed to be appointed by the state legislatures instead of the People directly for basically the same reason.
I feel like the founders felt that the voting base would not possibly be dumb enough to support an individual like Trump.
That's actually one of the reasons we have an electoral college (though not the only reason, and I'm not claiming that any of those reasons are necessarily good, just that it was part of the justification for why our system is the way it is,) some of the founders were afraid the average voter might be too stupid to choose a decent president.
Of course a couple centuries of fucking with the system has made it backfire on us. If it worked the way it was supposed to, we would have had a bunch of faithless electors take a look at who the people of their state voted for and say "hell no."