You ask for an explanation of ‘what these people think’.
You have obviously never asked any of ‘them’. Try it. Too many of ‘us’ ignore ‘them’ and dont talk to them at all. In fact many of ‘us’ walk past ‘them’ without acknowledging them at all. They dont bite, and you dont know what a difference a nice hello can make!
The answer really is tinok shenishba. They have been brought up that its not a big deal to drive on shabbos r”l and are just going to shul in the same way that they usually move around on shabbos to go shopping or to a football game etc. They dont understand why they cant do melochos because their parents, friends and community have been brought up that its ok and only old fashioned frummers dont do it. One guy said “but I have yartzeit on shabbos so if I cant drive to shul I wouldnt be able to get there at all, so which is better, not to go or to drive?” When I tried to explain why its not only better but imperative to stay at home rather than drive, he could not accept it. I just couldnt get him to see where I was coming from. Nebach!
But dont ignore them. You never know how your smile and acknowledgement can change their opinion of frummers.