The "left" had a laundry list of falsehoods Trump's campaign was built on and it didn't matter at all. The (completely fair!) discussion of racism and bigotry as part of Trump's appeal was far from the "left"'s only argument.

That's not at all a valid statement. People rightly pointed out, over and over again, the inconsistency of Trump's views on several issues. The trope that the argument was nothing but shouting about racism is just not correct.