Functional languages are inherently built on non-functional ones, for the same reason that object oriented languages are built on non object oriented ones, because cpus are fundamentally not object oriented or functional.

They are computational machines with specific instructions around moving values in memory and performing certain operations on them.

Assembly / machine code is always, at a fundamental level, procedural programming because at a the most fundamental level, cpus are designed as procedural machines, so all higher ordered languages, from C, all the way up through Python and Lisp, have to translate down to assembly, which maps to the machine's instruction set, which is procedural and imperative.

However, there is an OS that tries to be functional as much as possible though, and that's a Linux distribution called NixOS, based on the functional language Nix.