It's just their ego showing through.

It basically now comes down to the current devs depending on new Rust devs for anything that interacts with Rust code.

They could just work together with Rust devs to solve any issues (API for example).

But their ego doesn't allow for it. They want to do everything by themselves because that's how it always was (up until now).

Sure, you could say it's more efficient to work on things alone for some people, and I'd agree here, but realistically that's not going to matter because the most interactivity that exists (at the moment) between Rust and C in Linux is... the API. Something that they touch up on once in a while. Once it's solid enough, they don't have to touch it anymore at all.

This is a completely new challenge that the Linux devs are facing now after a new language has been introduced. It was tried before, but now it's been approved. The only person they should be mad at is Linus, not the Rust devs.