It doesn't particularly matter if a specific kernel module has a big community behind it. 3-4 motivated people would be plenty to maintain a module. The major part of a GPU driver is in userspace, not the kernel.

The kernel community have slowly started to embrace rust in recent years. Maybe the community is not so small as you think, or at least won't be in the near future.

Most hardware needs reverse engineering to work - we only got the opensource AMD GPU driver relatively recently.

Kernel work is niche in general so really you could say the same thing about Linux itself - yet here we are, it likely works on many devices you use.

Linus himself is using the work Asahi Linux has put in :)