I feel like it's mainly diagnostic of my basic awareness of how presidential elections work in this country, as well as my awareness that there was some amount of controversy over who "actually" won. Also, there is some subset of people who would get the question right with incorrect reasoning.

There is an extraordinary mass amnesia about 2020, with a LOT of people on the right attributing events and policies (covid lockdowns, BLM protests, etc) to Biden. It isn't even in bad faith, they genuinely forget that Trump was in office for the entire year.

For sure, just like happened with Obama and 9/11, but even more widespread.