He got 2.3 million more votes than Harris, which 1.5% more than her for a grand total of 49.8% of the vote. Almost 2% voted 3rd party, which basically means they didn't vote in FPTP. That still doesn't mean a majority voted for him. Both Obama and Biden won more than 50%, so him not breaking that threshold in either election he won was noteworthy. He's always been the most popular of the unpopular.
And all the ones that didn't vote who could have, were OK with Trump winning, or else they would have turned up to vote against him.
You're not wrong on this point, at least mechanically. Unfortunately for all of us who understand this, most people are don't view voting this way. They lack the imagination for an election meaning the death of liberal democracy. Many who sat out might not have thought Trump would win. They thought even if he did win, he'd only be as bad as his first term, which while bad, could still be passed off as more of the same. Even to this day, people still think we live in a nation of laws, that things will go back to normal next election, that we aren't doomed to decades of instability where nothing is off the table.
I really don't blame them for thinking this, as a Democrats didn't really campaign with the desperation they needed to. They tried a new way Democrat approach of appealing to the middle, thinking the left was secure. They didn't harp on project 2025 or Trump's open promises of dictatorship. They didn't want people to panic, to realize how fragile things were, to realize that the rich donors they served were already on Trump's side. They made everyone, even the loyal voters like me, feel like we had no choice in policy. They made clear that their promises of promoting democracy and regulating capitalism were lies. They made it as hard as possible to rationally support them, so I'll never blame those who didn't vote blue more than I blame the Democrats.
You are correct that Americans failed to prevent this; that everything we see is our collective fault. However, most don't want this. Fascism taking power doesn't mean it is popular or what most really want. It's stupidity, not malice.