Why did the first generation of stars have to be extremely massive compared to current stars?

Answer

The gas remained relatively hot for much longer due to inefficient cooling

Because the early gas could not cool effectively without heavy elements, the entire large collapsing mass had to reach a critical density before fusion ignited, leading to exceptionally high required masses for collapse.

Why did the first generation of stars have to be extremely massive compared to current stars?
Spacestarscosmologyformationastrophysicsnebulaestellar formation