Be honest, Trump IS NOT a legally elected president, but an appointed one.
Hillary got 3 million votes more than Trump!
What you are right of course, but the fact is that if the electoral system will work as you say, a few cities will make the decision for all of America. It's not quite right. As a financial center like new York can solve the problems of farmers of Texas? Therefore, the vote of a simple majority does not reflect the mood in society.
But if there are really such evidence that the voting passed illegally, then I believe that America's state, with a civilized and fair court, can hold a hearing to rectify this error. After all, are there legitimate reasons for re-election or do something in this case?