Why Is the Universe Mostly Made Out of Red Dwarfs?

There's this concept in astronomy called the initial mass function, which tries to describe basically how much stuff a star gets. And as gas clouds are sort of coming together and forming stars, you're just less likely to grab a bigger blob of stuff. You're more likely to form multiple smaller stars than a single larger star. People aren't sure exactly what the shape of this initial mass function is, but we are sure of the overall trend that bigger stars tend to be more rare and smaller stars more common.