GIL removal is easy. The hard part is that locking all the structures in order to avoid interpreter crashes (which are not acceptable in a language like python)

GIL removal is easy. The hard part is that locking all the structures in order to avoid interpreter crashes (which are not acceptable in a language like python) is hard. It's not impossible though, jython did that. CPython additionally has a hard-to-remove refcounting GC strategy which makes it really hard to do any sort of GIL-less CPython without a major performance hit on locking every object at every refcount.