What if the "Global Interpreter Lock" needs to be removed for JIT?

It doesn't. PyPy has a JIT and a GIL. The JIT just compiles the byte code to native code before running, along with some tricks that are over my head.

Edit: Here is PyPy's FAQ about it

https://doc.pypy.org/en/latest/faq.html#does-pypy-have-a-gil...