Feel a bit bad for Yomif Kejelcha who also broke the 2-hour mark, with this being his first competition marathon, but managed to neither break a record nor win.
There were recent tests (in France I think) in schools where 50% or something could not run 1 km (sorry I don't have the details on mobile). These are children who have infinity energy (source: parent).
A typical adult won't make it to 1km (source: going back to sport and dying on a 2.5 km run)
I'm... dubious of this. At 39 I started running, for the first time in my life, ran 5km, didn't actually die, and went from there. I'd think most adults could manage 1km, anyway.
I used to play volleyball a lot at the university, and then at a business league (we were horrendous, but anyway :)). Then I travelled a lot and let myself go.
So I started to commute to the office by bike, about 15 km each way, 5 days a week for two years. I had a puncture and decided to run the remaining distance (about 2 km) because I was late. After 500 m my lungs were on fire.
55 now, I restarted this year sport to do the smallest existing triathlon. I was already biking a bit and "just" have to do the swimming and running. I am at my 10th or so run of 2.5 km (I try to do it 2 times a week) and I am dying several times on the way. The fact I make it back home is religiously miraculous.
I am not an athlete, far from this. I am not the extreme obese either. I am somewhere in between, like are most of the people I know (of different ages). I do not see them running 1 km strong (let's say right above trotting)
Ah - and I did the whole battery of medical tests to make sure that I will not literally die when training. I am in a very good shape, heart wise.
It's easier to draw attention (and therefore sponsorships) if you leave some room to improve on successive attempts. It's riskier to give everything up front and then risk plateauing or regressing in your subsequent attempts.