The winner was periodically dosed with strychnine mixed in brandy, and suffered hallucinations for the last 10 miles of the race, was carried over the finish line, and would have died if doctors didn't immediately treat him.
Another competitor hadn't eaten in 40 hours, so he stopped at an orchard and ate some apples that turned out to be rotten and gave him incredible stomach pains, so he had to lie down.
Another competitor almost died from the dust clouds kicked up by the cars driving ahead and behind the participants.
Another competitor was chased off the race by aggressive dogs.
Just so many crazy things all at once.
There's a fantastic episode from The Memory Palace about the race:
https://thememorypalace.us/2010/02/episode-26-citius-altius-...