I don't think it's about public opinion so much as pushing the goalposts. The whole erosion of privacy since the 60s (maybe further but at least since then) has been a 'boiled frogs' situation.
What I think the endgame is here is to be able to do surveillance out in the open, so you can have more human resources doing it, and so you can use that surveillance legally more often. If you have a clandestine surveillance operation, you can only employ people you trust not to squeal and you have to engage in parallel construction (or resort to extralegal execution of force).
A lot easier if you can just point to a piece of paper and say "but you said we could"
What I think the endgame is here is to be able to do surveillance out in the open, so you can have more human resources doing it, and so you can use that surveillance legally more often. If you have a clandestine surveillance operation, you can only employ people you trust not to squeal and you have to engage in parallel construction (or resort to extralegal execution of force).
A lot easier if you can just point to a piece of paper and say "but you said we could"