Those politicians who are vocal against mass surveillance tend to change their tune the moment they're in office and I doubt they were all intending to go back on their campaign promises from the start or that they were really convinced by horror stories of terrorists told over powerpoint in closed door briefings.
I wouldn't doubt if they were also giving politicians examples of the kind of dirt they already have on them and their families. This is one of the biggest risks of the surveillance state. Endless blackmail material made up of actual skeletons, as well as the resources to install new ones into anyone's closets whenever needed.