Legislators passed the 22nd Amendment to prevent future presidents from trying to beat FDR’s record of 12 years in office. That’s why former presidents who served two full terms are disqualified from serving again. (Interestingly, the wording of the 22nd Amendment says that no person can be “elected” more than twice for president, but it doesn’t explicitly prevent a former two-term president from ascending to a third term via the vice presidency.)
Sauce:
https://www.history.com/articles/what-are-the-qualifications-to-be-president-of-the-united-states