I do not know why you would question that, motorists who were going faster than the arbitrary set limit, were low hanging fruit. That is obvious.
And terrorists kill relatively few people so hardly surprising many other things in life do more. It is not a reasonable comparison.
Whether the speed limit is well publicised or not (and umpteen changes down a stretch of the road is hardly well publicised) is not relevant, so your general insult about being stupid is inappropriate also.
Furthermore there are folk out there now so concerned about the ridiculous limits applied these days that they are permanently crawling along in case they missed a change, and feel so obliged to watch the speedometer they they are inevitably distracted from paying attention to other driving necessities and miss signs, lights, etc..
It is the madness of a controlling authority who fails to perform in the interests of society because they want what they want and the society they are supposed to be serving is clearly considered unimportant and just the means of having control.