This is actually even worse than one great big file (which is also suboptimal, of course). Navigation becomes extremely painful. Multiple files with the same basename proliferate. New hires find the structure impossible difficult to master. Imports and boilerplate dominate actual code.

The worst part is that it's hard to get familiar with any file when there are so many of them.

In my experience, the optimum size for a Python file is between 50 and 250 lines of code: enough code to actually accomplish something substantive, but not so big you can't understand the whole thing.