I think if everyone agreed he lost you would be right but if the election is at all close I doubt there will be such agreement. What does the secret service do if the president says the election was stolen?
The Secret Service is very much part of the dreaded Deep State. Their loyalty is to the Constitution, not the man in the office. When the winner of the electoral college is official (Trump has no control over that) they'll begin their own transition to a new president. The rest of federal law enforcement & the military will fall in line right behind them.