The NSA is incapable of building the type of mass surveillance infastructure we see today. That infrastructure is built and maintained by private tech companies. The NSA comes along repurposes that already collected data to their own ends.
Further, the NSA's usage of said information has never been linked to any population wide mental health crises, unlike big tech.
There is also a wide range of work the NSA does, and most people working there don't know much beyond their own need to know.