I'd bet a lot of money that the NSA didn't just turn off their servers and sit their twiddling their thumbs after the Snowden leaks.

I think the intimation is that it's not only the NSA or the United States building such databases, and the assumption that the NSA would have the largest database may no longer be credible--not because they stopped gathering data but because they were surpassed.

That's an unfair caricature. The steelman version of that argument is that China has likely amassed a more robust global surveillance database (to the extent that that's even the right word to use) than the U.S.

I think it's just true in a literal sense that China has constructed it's own surveillance system that under any metric would be larger than that of the United States or any other nation.

So why then are so many BigData job offerings at those US agencies? I am speaking of hundreds and thousands here...

Are there really that many job openings?

Just search for all current and past "data scientist" / BigData job offerings for those agencies on Google and Archive.org for the last 10 years. This data is freely available.

Source on number of openings? You can also do a lot of data science/engineering on open data. There is a huge amount of open data out there.

Edit: Downvoted for a question. Keep carrying on with the idiocy.