Writing the umpteenth Javascript framework might be good for your career. It isn't hard, in fact, it is so easy a multitude of javascript-only developers attempt it on a regular basis.

Occasionally one takes off. Really just a function of how many friends the author has, their stature in "the community" and/or their aptitude for creating cute marketable landing pages.

There is a multitude of people capable of jumping in with hot takes explaining why the new framework is superior/inferior, tweets, blog posts, courses abound..

In contrast re-inventing git is hard. Few people can wax poetic about the differences between alternatives. Even fewer can come up with a new one. The audience is far smaller not to mention skeptical. Less profit in it.

Rather the difference between a new age cult/mega-church and the Catholic church.