People in their early 20s are also much less likely to have other responsibilities "intruding" into their headspace. It's a lot easier to be monomaniacal when you don't (for example) have kids yet.
I know. That's the common argument, but I don't think that's it. See the argument I made in the previous comment. As I wrote in that comment, Magnus thinks his brain was better when he was younger. It probably doesn't help to have responsibilities like children, but I don't think that explain everything. There are also many people without children for example. And if you don't have children then studying full time should take as much if not more time than a simple job.
Also, Hans Albert Einstein was born during Einstein's miracle year.
> Also, Hans Albert Einstein was born during Einstein's miracle year.
This was in an era when fathers had little to do with childcare. I don’t know about Einstein’s specific situation, but even 40 years ago almost half of fathers had never changed a diaper.
