Something is not right here.

Why would a JavaScript framework outperform a C++ or a Rust framework by a factor of 30 when JS as a language is at least half an order of magnitude slower than C++ or Rust?

Writing your Web server in a compiled language ads considerable difficulty, but the reason people do it is to get the serious speed up, and reduce the memory footprint.

Unfortunately, I don't know Crow or Actix or Express, but my theory is that there's some sort of caching turned on with Express that isn't turned on with the other two. (I don't expect Django to perform to the speed of compiled frameworks.)