I think that early on, people started using Python because they liked the language, before they used it for numerical computation. Many people were satisfied with an installation of Matlab, C, or whatever, on their desks. But they started using Python as a scripting language, before asking: Wouldn't it be nice if we could use Python for everything?

For instance in my own case, my first use of Python was outside of mainstream scientific computing. I needed something to install on lab computers, for data acquisition and automation. And it needed to be free because my employer was under a spending freeze after the 2008 financial meltdown. Oh, and I also wanted something for hobby projects, that would be equally at home on Windows or Linux.

So I think the quality of the language came first.