PyPy is a python implementation in python (RPython to be exact)

No it doesn't. As someone else mentioned, RPython exists, and in general, bootstrapping is nice, but there are a variety of compelling reasons to not rewrite CPython in python, that have nothing to do with it being "suited" or not.

History, reliability, simplicity, lack-of-value, etc. At this point there's not much to gain by rewriting cpython in python (pleasing some guy on the internet), and quite a lot to lose (simple c-interop) for what would be years of work by a lot of people.

It wouldn't have been years of work if they started right after Python was first implemented instead of a big-bang now. For 25 years each time they've implemented a new feature they've chosen C over Python to do it, for reasons of it being better suited, some of which you've listed yourself! Like simple C-interop!

I don't think it's a criticism of Python! I've worked on meta-circular implementations of languages and I don't do it for the sake of it. Not every language is suited for every task.

Right, but all of those are historical, not innate, which makes your comment wildly misleading.

If the Python ecosystem weren't c-based, it wouldn't matter. But it is. But that has nothing to do with python the language in a vacuum, and everything to do with choices some guy made 25 years ago.

You typically have to bootstrap your language in a different one. There are some languages that have since gone back and re-wrote the compiler or runtime engine in the same language (in those languages that need a runtime).