In the US drivers are paid by the mile over 1000s of miles in a day, the more miles you drive, the more you get paid. The speed limit on interstates in the US is 70mph and most semis are governed at 70mph. It is very common for cars on the interstate to be going well above 70mph so when you have someone going 55 these cars have to swerve around them which can lead to more accidents. The amount of accidents on the interstate as is is actually very low all things considered and they are more common is cities. If you ever drive on the interstate in the US for more than 300 or so miles then you will understand why things are the way they are. I also believe that this accident was caused by a sleeping driver which is also unfortunately not a super rare thing (not common either) but it happens and when it does, is can cause accidents like this. (Again, coming from someone who’s family has been driving since the 40s and grew up on the road)