As mentioned in the thread, mostly because at this point it's a massive block of battle-tested code. That's not something one scraps and rewrites lightly, and "

As mentioned in the thread, mostly because at this point it's a massive block of battle-tested code. That's not something one scraps and rewrites lightly, and "because I like a different language" counts as rewriting it lightly. The advantages of Lisp do not outweigh the disadvantages of a scrap-and-rewrite. A kernel with a goal of Linux compatibility is another matter entirely: something in Common Lisp or Go or Rust or some other language could make for a very interesting project. But if someone were to design a kernel from the ground up with this goal in mind, the internals would probably not look all that much like those of Linux. Whether or not that's a good thing is left as an exercise for the reader.