Answer:
Because he left office peacefully and willingly.
By being the first president to leave office this way, he set a precedent and marked the first peaceful transfer of power between upcoming and current presidents. Since then, the loser of presidential elections has willingly and peacefully surrender power to the winner.
When Dwight Eisenhower sent federal troops into Central High School in Little Rock, Arkansas in 1957, it demonstrated that the President could assume powers to make unilateral decisions in order to ensure that the states did not descend into chaos or any disorder
The answer that would make the most sense is bipolar disorder.