I think the case is simple here: Racket community was not capable of producing good programming language, so instead they decided to take someone else's better

I think the case is simple here: Racket community was not capable of producing good programming language, so instead they decided to take someone else's better implementation: they decided to abandon the years and years of their efforts, because they realized that Kent Dybvig (a real hero i this story!) was better than all of them. That's why they decided to take his Chez scheme and parasitate on his effort. The very fact that they did this tells us a lot about Racket's community “achievements”!