I suspect people like that don't properly understand the difference between relative speed and absolute speed. Because they are moving faster, they perceive other vehicles as stationary objects that won't move. They assume weaving through gaps will be safe, they think they have a right for it to be safe, and boy do they get angry if they are proven wrong, when one of those "stationary" objects has to swerve to avoid something.
They make the same assumptions at slow speeds, assuming slow-moving vehicles cannot change speed/direction suddenly. Whenever they are moving faster they assume an attitude of superiority and entitlement.