When it's 2020, the other guy is trump, a pandemic is killing hundreds of thousands of Americans, and the Donald is comparing it to the flu....... It is incredibly easy to vote for the other guy. You also might vote based on dem vs repub policy differences.
But ya I'm not sure if he was actually super popular.... Seems the only time he polled above 50% was shortly after he got elected.... and ever since then it has declined and bounced around 40%. Obama smoked him in the polls........ Sure, Obama had less total votes but there were also less total voters at the time.