Well, you said it's "odd" if people don't trust Trump, since they voted him in. I'm saying that plenty of votes may have been because they trusted Biden even less. In a 2-party system it's difficult to distinguish between "I want A" and "I really don't want B".
US, UK, Canada, and Australia, certainly. But almost all European countries are multi-party. I suppose there's an argument that some voting systems are "more democratic" than others, in the sense that they allow/incentivise individuals to express a more accurate picture of their desires via their vote.
That's fair. I know most Western countries are effectively 2 party, but the US does seem more so than others. Regardless, he is who was picked by a very large number of people in a fair, democratic election.