Lambda calculus is a lot simpler than Python. It bares a striking similarity to Gentzens natural deduction rules and is essentially isomorphic to it. It is also very well studied and its properties are well known. Hence it makes an excellent basis for a programming language. The idea that Lambda calculus was discovered and not invented was recently entertained by Phil Wadler. Given his academic credentials, I think we can assume he knows what he is talking about.
Why can we assume that? Is he an expert on the history of logic? That he's an expert in an adjacent field doesn't make him at all an expert on that. If you listen to his talks and compare with the actual texts he mentions you'll see that he's wrong.
And the similarity is not "striking" at all. It's by design. It is only striking if you don't know the actual history of how these formal systems developed. A couple of years ago I composed an entire anthology on the subject: https://pron.github.io/computation-logic-algebra
