It's not only because of data science of machine learning. Big, high profile projects are being done in Python (eg. Openstack).

I am at a big company, and it seems most new projects are being done in Python. No one asks why, it is just accepted.

Now the question is why. I have no explanation, other than maybe that's because universities have been teaching python more often, and it happens to be practical.

I just wish everyone were using Python 3.