Because the ecosystem is mostly built by people with no formal education and little experience -- they're literally re-inventing everything from the history of computer science.
Or perhaps because the ecosystem is built by people with much formal education and industry experience applying traditional computer science paradigms to a stack with bizarre and unconventional tooling, not realizing it was made by other experienced backend developers attempting to fix the same imagined problem in a domain they don't understand. The outcome would be the same, so it's hard to say for sure.
Many people will learn JavaScript this year as their first language. Those are not the people writing the successful libraries like React.
Lots of people with little experience contribute, which is great, but "the ecosystem" is largely built by people with plenty of experience and training.
