What your watching is a race with the top RC drivers in the world.
The passing you see are other top drivers making line adjustments letting the top two drivers (Mayfeild and I think that was the Drake) race by. There are even two situations you can see drivers pulled way off and just about stopped really close to the hay bails. Once one the back after the table (yellow car dn time 2:21) and another driver at the beginning of the front straight (white car dn time 1:44). One car took an outside line down the straight and slowed enough to let both pass (dn time 2:34).
They all moved off the better line to let the two leaders pass.
-Don