It says “if the president elect shall fail to qualify” or something like that. Once they’re president, that’s that.
What obambam, in his evil brilliance, noted was... this takes place AFTER the election. So the onus is on the SCOTUS to throw out election results AFTER a black dude is voted into office, risking widespread racial riots. So the SCOTUS took a pass.
At least in Obamas case, one of his parents was a US citizen.