The need here is bootstrapping. If mold is written in Rust you cannot even compile it.

Even Rust is written with Rust. But yeah, if you want to bootstrap absolutely from the beginning, I see the issue.

	▲	lrvick an hour ago \| parent [-]
		We regularly and redundantly full source bootstrap our entire tree from 186 bytes of machine code due to a supply chain security policy that forbids trusting any single human or computer.