A. He was rather illegitimate, because of a system designed to make slave owners happy enough to sign the Constitution of the United States by giving them more vote power despite having fewer votes. Other than that, unfortunately it’s how the law works.
B. Yes, unfortunately too many foreign powers attempt this, but so far none have been proven conclusively to work directly with any candidate. Only a bit of evidence from the 2016 election that Trump’s campaign was.
C. The only indication I saw of Trump’s popularity with any of those groups was Trump’s claim that they all really love him.
D. And not a single shred of evidence actually presented about any claims of voter fraud. Only repeated claims of fraud without evidence, and a few evidenced claims of fraud quickly shown to be Trump supporters faking it. (Burned sample ballots, anyone?)