Somebody I know (not in tech) wanted to switch from Windows to Linux and I said:
"Which one?"
It's the same as Mastodon.
"Which instance?"
The answer is usually the biggest / most popular instance or distro, but not many applications the masses use are on Linux, the same as there is not many interesting people on Mastodon for people to switch over to it.
Applications are the barrier to mass adoption here for Linux unfortunately, and the paralysis of choice is the double edged sword for the massive amount of Linux distros.
Thousands of years of effort spread across many distributions that not many people would use.