“...voting on the basis of fraudulent votes.”
The date came, O-h, and their job was to vote. The voting slates were activated in each state based on the verified (though in some cases, suspected as fraudulent) vote counts. And they voted, on schedule. Yeah, some states, some critically important states, activated Biden-aligned electoral slates based on fraudulent vote counts, but that fact was not legally known as of the date for the electoral vote.
Their job is explicitly stated in state laws. If they vote for fraudulent votes, those votes have to be decertified. Not all states have identical laws, but many are identical.