Quite often in road racing cyclists will create a C-shape curve on the road, following the path taken by the peloton leader.
The peloton leader seems to create this curve because they're looking behind them (for some challenger they're tracking in one point classification or another, perhaps—could there be any other reason why the leader creates this path?).
But then the rest of the peloton follow the track. I have trouble imagining that the benefit of drafting is so high it outweighs the advantage of cutting it short and continuing straight. This is not quite a circle, but if it is, the extra distance is as much as 3.14/2, or 57% longer.
Why do racers follow the leader in a curve rather than take the shortest path?
Speculation #1: Might this be a sudden side-wind draft that forces everyone to lean (to the right in this case) and then turn to accommodate the leaning? If that's the case, why do they not stay (on the right, in this case)? Why do they return to the left of the road? (The road is closed for them.)
Speculation #2: Might there be an imperfection on the road that they can see, but that we can't see in recordings?
Speculation #3: "Everyone arriving within 3 seconds of another cyclist is awarded the same finish time." This rule was introduced (in 1953?) to avoid an entire peloton fighting for a slight improvement in ranking at the finish and taking undue risks of crashing the peloton. Might this rule also act here to eliminate the incentive of improving ranks?