Why was FDR allowed to serve four terms? (Short Animated Documentary)

 

FDR (whose name isn't Frederick) is the only US president to win a third term and stay in office for over 8 years. The two-term limit wasn't introduced until after he had snuffed it so why didn't any president before him manage the feat. To find out watch this short and simple animated history…

Source: History Matters (2023-02-24)