> 2 years?

Half of the items, and almost all in the "Mathematics" section, you would have learned during your BSc/MSc (if it's in applied math or physics, and Python programming is your hobby). I can't find the author's CV, but there is 5 years from him returning his MSc thesis in 2017 to returning PhD thesis in 2022. Maybe he studied ML for all those 5 years, or maybe he took off 2 years to travel the world, who knows.

You can learn a lot when you’re in your early 20s, single, ambitious, and getting a stipend from a university to do nothing but study for 16 hours a day.

I was about to comment on the short PhD in "2-and-a-bit years" -- and how the UK expectation for PhD program duration is so different from in the US.

And it wasn't to say that he's a genius. It's that the program is planned to be shorter, and in fact, there's less funding available to go longer even if you wanted to.

In the UK, 3 years is common.

One must consider what he spent the previous 22 years doing.