Even Torvalds said that a lot of critical parts of the kernel are completely undocumented and only one or two devs know how they work. IMO that's completely unacceptable, especially for such an important OS. They've proven they don't want to collaborate or communicate how they work to others.
Rust encodes a LOT of things into the type system, which makes it far, far easier to maintain since you don't need docs, and since the compiler enforces these things automatically. Memory safety is only one of them.
Starting something in a modern language instead of one with so little safety is a massively important feature.
The difference is similar to gas vs electric cars. They're both ultimately cars. Gas filled the niche that horses left. Electric cars have been taken seriously for far less time than gas, but their better technology has accelerated innovation. They almost never need to be taken to the mechanic, don't need oil changes, are way better for the environment, etc. and basically the only gap is getting batteries with larger capacity and more charging stations. We'll get there soon, and then gas cars will be fully obsolete.
In the end, someone who just sees them as one car vs another doesn't understand all the benefits of the implementation.
Why? Not making the connection.