Seriously what else is he supposed to do? Everyone hates him already so why not do everything you can to try to keep power?
At this point we need a better word than unprecedented. I use the word "objective" a lot, probably because I don't expect to change political views, but I do believe that no matter your views on policy at the very least we can try to apply some objectivity when discussing these matters.
Objectively, the near total failure in courtrooms across the nation should be a pretty clear indication that the legal claims being made by Trump's lawyers are incredibly flimsy. Fraud exists and should be addressed, but what Trump is alleging in public as "rampant" or "widespread" in fact lacks substantial evidence. Objectively, Democrats wanted to prove Russia collusion, but lacked evidence. I don't see this as being any different.
From what I can gather, the legal argument with the sturdiest foundation appears to be regarding who has the authority to set election rules. And it's possible that Trump would have won that argument had he filed suit before the election. He had months to challenge the rules change in Pennsylvania, for example, and he didn't. To emphasize the point, several decisions against him cite "a complete failure to act with due diligence."
Bottom line, and objectively, Trump is arguing the votes of his rival should not count based on widespread voter fraud, which he has failed to prove, and laws that he had every opportunity to challenge before the election, and failed to do. Judges, even his appointees, describe the remedy his seeks as a retroactive attempt to disenfranchise millions of voters who cast ballots according rules provided by their states.
We can debate the merits of democracy, but assuming that most everyone in this forum believes in democracy, what Trump is attempting to do is decidedly anti-democratic.