Python isn't slow at all, provided you hold it right. Pandas/Numpy are pure C libraries under the covers, provided you are dealing with it not row-at-a-time. PyTorch etc drop down pretty much immediately into C (and the GPU specific libs). Python is just kinda binding it togther.

One of the reasons Python gained so much traction so quickly was easy integration with C. Using FFI, I can open and call C functions from a share library in about 5 lines of code. Plus python has very readable and straight forward C code itself, it's not that hard to make "pure C" extensions to python.

And now optional typing in Python allows for great JIT compilation, so even the pure python parts are getting quicker.

Most importantly: Python is blazing fast where it needs to be, developer speed. Scientists and engineers are the expesnive part.