The OP is absolutely correct in their facts, the guy can't just say "NU UH I REFUSE" if it's as cut and dried as a huge landslide loss.
However there's really no system in place stopping Team Trump from contesting election results in various states for months and months after the election if it's even reasonably close in any states. With enough GOP governors and judges in place in various states, Trump definitely COULD throw a giant legal wrench into everything and bring the process to a standstill for months and months while we all fucking groan because it's obvious the inevitable outcome is "he lost".
The 2000 election wasn't conceded until Dec 13th, just short of a month before the scheduled inauguration. And that was between two relatively "normal" candidates over a legit close race in Florida that definitely warranted a recount. Imagine instead of just Florida we've got recounts and court cases and appeals going on in 5-6 separate states and the chaos THAT is going to entail. These boobs won't even comply with subpoenas from Congress, they're not going to sit back and just say "Oh well the Supreme Court of Wisconsin said we lost, I guess that's it". They're going to appeal and appeal and keep the ride going on our dime.
Then after that expect Trump to just be in the news constantly, he'll be a regular on Fox News, probably have his own show there, maybe start his own news network as rumored in 2016, who knows. But he definitely ain't gonna ghost out and just show up at random sporting events over the next several years like past presidents have...
Out of all the fantasy scenarios, this is probably the one with the best likelihood of happening. Their overall strategy is stifle the vote, contest the vote, and litigate the vote both in courts and on Fox News. I've no doubt that they'll be yelling about all kinds of shit for as long as they can. But one thing is for sure: On January 6, 2021, Congress counts the electoral votes and names the next President who assumes office on January 20, 2021. There isn't a scenario where this doesn't happen.
For the conspiracy theorists:
The reason it will happen is because for all of the bluster, and the prevarication, and the shady dealing, and putting Party over country, those Republican senators and most of those Republican Congressmen also value the actual legitimacy of their offices. Sure, they'll try to exploit every gray area in the book, and forsake all norms, internal rules, and gentleman's agreements to get their way, and they will no doubt talk a lot of shit. The hyperbole will be through the roof, but they won't actually
do anything, because if they fail to actually implement the Constitutional mechanism that's clearly spelled out in the document that legitimizes their offices, then they're no longer legitimate themselves. That is foundational. That is bedrock. That is the implicit understanding that underlies everything. It would be an act that would directly lead to the dissolution of the Union itself, because there are a significant number of States who would take issue sending money and representatives to a body that is no longer the legitimate Constitutional government of the Union that they belong to.
Now, are these Senators and long-time Congressmen, who've seen Presidential administrations come and go, and who make a really good living by monetizing their offices, really going to threaten their gravy train for that? A close, contested election means one thing for them: they can make a
shitload of money off of it as their focus turns to the mid-terms. The amount of donations they'll receive will be monumental. They'll be in demand to speak in front of conservative groups, charging thousands of dollars per plate. All of the conservative grifters online and on the conservative news outlets will feel like they've won the lottery as their righteous fury drives revenue. Why would any of those people give up the enormous amount of money they're going to make over this?
This doesn't even get to the Courts, the institutions, and the actual Armed Forces, who are not going to turn their back on 200+ years of tradition, fidelity, and their actual Oaths for a baboon who would backstab any one of them on a whim.