1: you did not pass fast enough and lingering, the driver said fuck you.
2: Terrain is a key player. Hills are a bitch with heavy loads/ Under powered vehicles.
3: Governors are commonly found on big things.
many are well below 67mph. when 2 trucks try to pass with the same governor. either 1 has to back off ( yeah right 
) or just have to be patient.
4: big trucks speed up for a uphill approach. THEY ARE NOT FUCKING WITH YOU. driver wants a run for the hill or they will not maintain a decent speed and put on the flashers belowe 15mph below posted speed limit.
can’t simply give it fuel in the middle of a hill like a car.
truck who cannot maintain a decent speed going uphill. snarls traffic behind them. then everyone jumps lanes.
5: driver pulls out in front of you. welcome to our life, you do it too us. your dead and we live end of situation.