Being in uncharted territory as things often are with Trump, the Colorado Supreme Court had to construe the meaning of certain words/phrases in Section 3 of the 14th Amendment before it could apply Colorado law, and SCOTUS certainly has the final say as to what the U.S. Constitution says/means. That includes the question of whether Section 3 is self-executing or whether it requires an act of Congress (which act is not currently on the books). Then there are other issues like the applicability of the First Amendment and whether due process was afforded.
The decision is loooooooong. There are many moving parts (and plenty of uncharted territory), and thus many avenues available for SCOTUS to overturn it, if it is so inclined. They'll do a simple up-down vote, and then the majority will figure out why later. My understanding is that the part of the state's election code that allowed this case to be brought is basically unique to Colorado, so the Court could affirm but effectively limit the scope of its decision to the application of the specific Colorado law at issue.
