I haven’t had to take a DOT traffic flagging and safety class for a while but I can def tell you that the truck parked where it is is the first line of defense against a vehicle slamming into a work zone. They are supposed to be deployed a distance away so that upon impact it doesn’t get pushed into the work zone. Not sure what the required distance is between crash truck and work zone. OSHA and other rules set that.
As far as lane closures, that might almost depend on work and time of day and the permit. There are rules for when work zones along highways can be set up during certain times of the day. Lane closure might not have been permitted. We can’t see the signs set out indicating what kind of work is being done and if there were arrow boards and so on.
So that video doesn’t give all the info for how well the crew set up that work area and if they followed proper protocols.
This could be where the safety crew set up as needed and this was just a rare type of accident that no amount of prep could have stopped.
Blame needs to be put squarely on the two drivers for how things played out. Speed, lack of awareness of the work zone, failing to maintain safe distance, improper lane change and any other factors