How can the election be valid if the person running for president was invalid? If nothing else...McCain would be president and Biden Vice President, maybe?
You forget that the electoral college elects the president.
We elect electors. They haven’t been disqualified.
Electors elect the pres & veep separately on independent ballots.
Biden was elected to veep Constitutionally, and he’s qualified to be president, as far as we know.