Both major candidates optimized for the electoral college. If the election were on popularity they would have optimized for such --what the result would have been is unknown, it may have been the same or it might have changed the outcome, but we do know that the campaigns would have been vastly different.

Also, one candidate spent twice the amount on advertising. If the winner had outspent the loser by 2x, I'm sure there'd be an outcry about the amount of money used in the campaign.