tl;dr Language evolution and future outlook are big factors besides the existing language features themselves.

I guess Rust has attracted many C++ devs because C++ is painful and there were no other/better options. Rust comes with a build/dependency management system and memory safety guarantees on top of the type safety. Even though C++ templates are still unmatched, I prefer Rust 95% of the time. C++ is evolving very slow and it's extremely hard to participate. Rust will win that race eventually.

Python has been around since 1991(!) and it took a looong time to build the community. It was a niche like Nim is now for many years.

I'll definitely keep an eye on Nim because it has the potential to become quite popular.

Again, that's all just my opinion.