You might be in a bubble. Outside of a few US cities and outdoorsy areas, when I look around, almost nobody looks like they are going to raid a tunnel system in Afghanistan.
https://www.businessinsider.com.au/cdc-american-obesity-rate...
And physical fitness shows you have the time, money, and discipline to take care of yourself, and it can't easily be faked, so it serves as a pretty good signal of those traits. I'm not surprised leaders would want to differentiate themselves using it, especially when you're trying to stand out in a crowd of people who have time and money, since discipline is the rare trait.
It's also objectively healthy to lift weights for bone density and strength, among numerous other advantages, especially in our sedentary lifestyles. And the standard abdominal fat/beer belly is incredibly damaging to one's health, so if your goal is to stay healthy through your 60s to 80s, I welcome being "fit" as a fad.