A star’s mass gives a measure of the amount of “fuel”, and its luminosity gives a measure of the rate at which this “fuel” is consumed by nuclear burning, so a star’s lifetime is proportional to its Mass divided by its Luminosity

Start from BigBang, the Universe generates H and He, H fusion generates He and forms the very first stars with mass ~ 100 mass of the Sun. The more massive they are, the shorter lifetime they have (a few million years). A few million years is not much for a cosmic time scale which means they exploded pretty quickly as gigantic supernovae. They are called the 1st generation of star.

Over time these stars are gone but they left behind all the heavy elements that they had made during fusion processes up to iron and gas. These elements and gas could clump much better to make small next generation of stars.

In 2nd generation, there are more stars with different mass created spanning from low-mass (0.6 - 0.8 mass of the Sun). Due to the low pressure and temperature slowing down the fusion process, these stars have long lifetime (15-20 billion years).

This process happens again and again as there are more stars, more supernovae, and more chemical elements are made. This also leads to the formation of larger structures, such as our Milky Way.