I’m not sure why they feel it’s Linus’ responsibility to make Rust happen in the kernel.

That's not what's being said here, as far as I can tell. Linus is not expected to somehow "make Rust happen". But as a leader, he is expected to call out maintainers who block the R4L project and harass its members just because they feel like it. Christoph Hellwig's behavior should not be allowed.

I'm not saying Marcan is necessarily correct, to be clear. It might well be that Linus chose to handle the issue in a quieter way. We can't know whether Linus was planning on some kind of action that didn't involve him jumping into the middle of the mailing list fight, eg contacting Christoph Hellwig privately. I'm merely pointing out that maybe you misunderstood what Marcan is saying.

Or fork it and make a Rust Linux with blackjack and hookers, and boy, will everyone left behind feel silly that they didn’t jump on the bandwagon.

That's what they're doing. But if you read the entire post carefully, he explains why maintaining a fork without eventually upstreaming it is problematic. And it's not like they're forcing their dream on the linux project, because the discussions have already been had and rust has officially been accepted into the kernel. So in the wider context, this is about individual maintainers causing friction against an agreed-upon project they don't like.