I have no doubt that if all the Federal courts called the election as foul, it would have overturned it anyway, whether they have the explicitly enumerated power to do it or not.
Bear in mind, that "deriving their just powers from the consent of the governed" thing is always a Trump card.
I think the only remedy were for congress to call it a bad election, not certify and then to proceed with each congressional delegation picking with its one vote the president in the house and the VP in the senate — once certified, that boat had sailed. What am I missing?
Once the Electoral College vote was held in mid-December 2020 and all the electors were counted, there was no legitimate constitutional/legal way for anyone other than Joe Biden to be inaugurated in January 2021. Period.