From googling and scanning some of the news articles.
1. At least 1 of them reports it as 58 miles, not 37 and he was on a mountian bike.
2. One had a picture. He loooked stocky and fit. Not fat, stocky, but that is significant if things are really hot, he could have had trouble throwing off heat.
3. It looks like he left his bike and wandered off the route and that things were called in by a non-ride bystander. Possibly the call made it sound like a drunk? (My thought, nothing direct in the articles, but disoriented, saying he is OK and then staggering into the bushes sure fits).
4. There were 12 (I think) ambulances 'on duty' but 11 were already responding to emergency calls and number 12 was on dinner break.
5. The really sad aspect, the ride had 3 ambulances on the route, the closest 2 miles away. It looks like no one realized he was on the ride and alerted the ride organizers.