Trump could lose and not leave. But Cabinet members who try to help face prison.

[Bayard]

3. I don't understand why this keeps coming up

"If Trump were inclined to overstay his term, the levers of power work in favor of removal. Because the president immediately and automatically loses his constitutional authority upon expiration of his term or after removal through impeachment, he would lack the power to direct the U.S. Secret Service or other federal agents to protect him. He would likewise lose his power, as the commander in chief of the armed forces, to order a military response to defend him. In fact, the newly minted president would possess those presidential powers. If necessary, the successor could direct federal agents to forcibly remove Trump from the White House. Now a private citizen, Trump would no longer be immune from criminal prosecution, and could be arrested and charged with trespassing in the White House. While even former presidents enjoy Secret Service protection, agents presumably would not follow an illegal order to protect one from removal from office."

https://www.theatlantic.com/ideas/archive/2020/02/what-if-he-wont-go/606259/

Barbara McQuade
Former U.S. attorney for the Eastern District of Michigan

She does go on to give alternatives, but this is the legal process that has thus far, been unused in our nation's history.