nitpick: 800m world record is 1:40.91
... the 800 is also not a race where the WR time is challenged on a regular basis. Championship 800m racing is a wait and kick affair which never lends itself to ultrafast times because the first 400 is loafed.
The scary thing about David Rudisha's WR set at the 2012 Oly was that it was a solo wire-to-wire: https://www.youtube.com/watch?v=YKEOjWEzVGs
That DOES NOT HAPPEN in championship middle distance racing. Does not happen.
Almost all middle distance records are set with precisely controlled tracks, weather, pacers, and racers to provide best conditions and drafting and temperature for the best times.
Rudisha showed up a the Olympic Final, threw down a gauntlet to the field, and blew them away.
You can see at the 500m mark of the video there were four or five runners who perfectly paced and tactically positioned themselves, where 999/1000 times the leader will fall off and get blown away by the chasers. What happens as a chaser is that instictive additional adrenaline surges as you chase down your quarry, and you're running through a draft for additional momentym.
At 500m, Rudisha accelerates and leaves these other runners, who perfectly placed themselves for the usual chasedown, and just leaves them in the dust.
Now consider he is losing 1 second a 400m without a draft/rabbit....
Also, I'd like to point out that the 800m is probably the most painful race of the track events. Typically you'll be well into anaerobic debt as you complete the first lap, and the second lap is allllllll pain. A typical 800m racer will hit 500m or so, his body is saying "HOLY SHIT STOP WHAT ARE YOU DOING" and that's when the racer ... has to kick and exert maximal effort for the next 200-300m.
Rudisha as I understand wasn't a rift valley tribesman, the usual source of Kenyan elite distance runners who have genetic adaptations to altitude and efficient oxygen use / high VO2. He was a Maasai from the central lowlands.
Just an amazing race.
Now, I'm also a cynic of Olympic level performance, but that's for another day.
RE: D1 recruits at 15:00/5k: the NUTS part of that is that 15:00/5k is barely competitive pace for elite MARATHONs these days (under good conditions like Rotterdam, Chicago, or London). So you get recruited for D1 for running a speed for 3 miles that an elite racer keeps up for 26 miles.
Kind of along those lines, a lot of people don't realize how elite rabbits have to be just to run the proper pace for 1/2 to 1/3 the distance. They can't really go under the top 50 in the world to rabbit, otherwise they won't have the reliable talent to run the pace even on a so-so day.