The Constitution did not say if 5 people decided to run, that the guy that got the most votes from that lot is “unfit” because the majority % needed to win would be less than 50%.
He won fair and square.
He also didn’t have a single vote south of the Mason-Dixon. He was president in the North, and only just barely that, winning Illinois with 53 percent, Iowa, with 54, Indiana with 51, Ohio with 51, New York with 53, etc.
He remains the only president elected with only 30 percent of the total vote, since South carolina was excluded from the election.