Because 365 of the Electoral College electors are Democrats committed to voting for Obama. If not him then they’ll vote for Biden.
See my Post #196 ...
I disagree with your claim that Obama's electors would be ruled ineligible. In 1872, Horace Greeley died after the election but before the Electoral College met. His electors were not ruled ineligible. They merely voted for several other Democrats, only one of whom had been on the ballot. If Obama is ruled ineligible there is nothing in the Constitution that prohibits his electors from still casting their votes for him. Or for Biden, or another Democrat. All that can come out of that is the election will go to the House who will pick a Democrat since they control 26 or 27 of the congressional delegations.