The reasons are simple:
1. Lots more help and examples available online for python compared to FORTRAN.
2. Python is performant enough, 99% of the time if you make even a vague attempt to appropriately vectorize your code and/or use the right libraries and techniques.
3. Solving a well defined problem in any language is easy enough. What's hard is getting to that well defined problem, and that often involves playing and tweaking with things until you wrap your head around the problem space. Python saves me a lot of time so I can iterate faster by avoiding stupid errors and having much lower boilerplate overhead where stupid errors can really propagate into hard to follow error messages down the line.
Python just is a lot more intuitive. I don't have to waste nearly as much time on off-by-one and other stupid errors because my indexing was fucked up. So I can spend most my time on thinking about the stuff that really matters rather than implementation details.
That said, I can write some lean and mean FORTRAN if I really need to, and I'm ok with c++ when I need to be too. In reality though, most of my workload isn't that computationally intensive, and even when it is, most of the hard parts have been outsourced to c++ behind the scenes anyway. I can't even remember the last time when my computational need was bad enough that I considered writing my own fortran.
Microcontrollers are a different story. Trying to use python for that seems like a dumb idea, but I know MicroPython is a thing, though I'm skeptical of the whole concept to be honest. You're so close to the metal at that point that why would you want to abstract it away?
Looking back over the span of 4 decades, one big change is that there is just more stuff, and the specific programming language is just a small part of it. An advantage of learning something like Python is that you can do more with it, quickly, thanks to the libraries.