I'm not a cycling fan, but that's a terrible analogy. Nobody is going to "take a dive" on a bike at 40 mph trying to draw a foul.
The overhead camera could be more telling, but it's obscured by trees at the moment that Cavendish loses balance. The evidence looks like Sagan did change his line slightly. It's open to interpretation (was Cavendish already going down or did he get help) but the overhead video seems to show a fair amount of contact:
https://youtu.be/rXwZczGqWls
But the other guy changed his line at least as much, at least in my limited understanding of it. After seeing it a bunch of times it looks like the two were trying to shoot the same gap and the guy that wiped out was behind the guy that got DQ'd so the guy in front couldn't possibly know another person was trying to shoot the same gap.