Pretty much what czinck said.

Python is much more popular in general, which makes it more likely to be popular in any specific subfield, for various reasons:

1. More chance that people who decide to do anything in ML already use Python.

2. There's better existing support for various ML-related tasks in Python.

3. There's a larger audience available for ML-related things in Python, therefore people think it's more worthwhile to code things in it.

etc.

I'm not the parent poster, but I'm pretty sure they're saying that because Python is more popular in general (the base rate) it's more popular in AI/ML/whatever circles because of better general support (more tutorials, more libraries, more people already know it before trying to use it for a specific problem).