My initial guess would be "because of the zero-cost abstractions", since I read "zero-cost" as "zero runtime cost" which implies shifting cost from runtime to compile time—as would happen with eg generics or any sort of global properties.

(Uh oh, there's an em-dash, I must be an AI. I don't think I am, but that's what an AI would think.)

I used em dashes before AI, and won't stop now :)

That's sort of part of it, but it's also specific language design choices that if they were decided differently, might make things faster.