Building a haystack to search for needles isn't free. If it's not delivering enough needles then people are going to be under pressure to end the program. I think a lot of people in government have smartened up to the fact that these things can be just as easily used against them if they fall out of favor and that having this sort of ongoing data collection could become liability if the wrong kind of people are in charge. The kinds of things Muller has chosen to prosecute certainly makes a lot of people in Washington nervous about their skeletons in the closet so there's less political tolerance of these kinds of programs than there once was. Snowden's leaks and greater public knowledge of these programs have reduced public support. It frees up resources to go after Russian trolls (or whatever), hunting terrorists is so 2005. There really is no way you can justify a program like this in 2019 (or so we hope), they've been proven ineffective and unpopular.