It's even more surprising to me given that Pandas is such a poorly designed library. (Apparently the guy who developed it was learning Python while he was writing Pandas.) I saw candidates make mistakes due to quirks in Pandas often. And quirks can be extra deadly with data science code: https://news.ycombinator.com/item?id=33797339 So overall it's a weird situation. I think a big factor is that a lot of data scientists are newbie programmers who are just piling in to what's popular & established.
This makes a lot of sense. I remember trying to learn Pandas before v0.24 and finding the syntax changing a lot between versions which just confused me even more. I later learnt some R and was blown away by how easy tidyverse, and even base R data.frames were to use.
It does seem that Python has settled into a niche as one of the mainstream data science languages.