Assuming the reckless driving of the AI, they should all be dead

Tell me about it - they constantly yeet themselves over bumps and into 30kph zones, as well as driving at top speed on cap NO MATTER WHAT SURFACE!

I think the devs made them corner badly to compensate because you can easily beat them once you get into a twisty Rio. But on the whole the positions are unpredictable.

Ouch! I thought I was in the Dakar Desert Rally forum, the second title, sorry.
I guess it could be because of the repairs, and many times the vehicles stopped in a curve or an accident and do not start again...bug or breakdowns in the vehicles

Yeah it's not unusual to find them just stopped dead in the road. I have no idea if the game is simulating repairing or it's just a bug. But the ranks don't change when I go past them so who knows.

Staggered starts. Your physical location on the course is irrelevant. The amount of time that has elapsed since you left the starting line is what matters. Same for your opponents. So if you complete a waypoint in less time than another competitor, you may advance to a higher position than him, even though he is physically still in front of you.