The real heatwave hasn't even started... it's forecasted from Wednesday/Thursday onwards, so it will hit the return leg. In my opinion, the issue is that a sizeable slice of randonneurs doing long distance events are always on the edge of failure... moving speed is too slow, waste too long at controls and tend to be rather overweight and unfit, as athletes. Inevitably, any small variation to the theme, being that more hills, more wind or more heat cause many of them to go into failure mode.
Hang on a minute, here you are saying that a lot of audaxers are overweight and unfit.
Then here, ere is also a clear lack of preparation, but not the kind of preparation people do, which typically involve killing themselves with an impossible schedule of overnight rides for months.
you are saying they are overtraining.
That's a load of negativity.
I know people from this forum who (back when I used to ride a fair bit), who looked sizeable, but could ride me into the ground anytime. I was consistently at my heaviest when commuting 250miles a week; the mileages demanded a lot of eating.
Your point about the need to sleep and quality training, rather than endless miles, is a good one.
They are not over-training... in fact they are not training at all... they are over riding. Guy in question (which is your typical audaxer you see at most events) would try to fit as many 200 as possible in his calendar in preparation for a 600... that is not training. When I was doing Audax, I was doing something similar, I never managed to lose a gram, despite riding maybe twice as many miles as I do know... we all know in an Audax we eat like pigs, all sorts of junk and then we continue to eat for the following days. I never got faster either... all I improved was my ability to suffer through a long day... in essence I became more patient, maybe more resilient, but ultimately unable to tackle something like MC1K... so not a smidge better than when I started. In fact, my first 400 was also my fastest by quite some margin.
A coach would probably look at what he does, try to put some structure in his riding, reduce the mileage dramatically, include more quality miles (speedwork), force some rest days and some short recovery rides and suggest a better diet.