The Florida supremes and their progressive activism is what caused the SCOTUS to become involved. That is also clear and codified into law. The SCOTUS could either hear the case or refuse and let the Florida supremes stand as law.
LLS
Except that SCOFLA can't make laws in Florida, AND the sole power to appoint electors rested with the Legislature, which was sitting and ready to act.
The appointment of electors, and the counting (certification) of their votes, are not within the scope of powers granted in Article III.
It's worth noting that the Federal courts actually got it right in another case that was making news a couple of years after that. I'm referring to the situation in New Jersey where a corrupt worm named Bob Torricelli was replaced on the ballot by that fossil Frank Lautenberg after the ballot deadline had passed. It was the subject of a high-profile legal dispute, and the Supreme Court eventually refused to hear the case.
Their rationale was sound, and it was the same rationale that should have applied in Florida in 2000:
The court basically said that even a blatant violation of state law like the post-deadline ballot change in New Jersey was not covered under Federal law. The only Federal statute that would have applied was the Voting Rights Act, and in the New Jersey case there wasn't a single person who ever claimed that the ballot change had violated his or her right to vote. In other words, it's not the job of the Federal courts to correct a fouled-up state government.