Why though? thats madness! I can only assume they are people who just like to argue and protest about anything and everything just for the sake of it without giving a toss about what it is they are fighting for
Can't speak for England, but here in Scotland they really picked up steam as a campaign group over the summer when we were told school was going to be 'blended learning' for the rest of the academic year, and 'blended learning' meant kids in school less than half the time, sometimes not even a third of the time. So UsForThem got a lot of angry/worried parents back then. I wasn't in the group but loads of parents I know were, it was turning up on my facebook feed all the time.
Then blended learning was dropped and schools went back full time, and most parents thought that was fine so didn't see the need to be in Facebook campaigning groups any more. So now it's shrunk to a much smaller group of people who are unhappy with the current situation, because they don't want kids wearing masks on school buses or whatever else. That's going to be a very different group of people and a very different kind of group.
I just looked at their Facebook page and they're discussing whether or not they'd take children out of schools if masks were mandatory in classrooms, so I'm guessing they're not THAT fussed about keeping schools open...