"NSA mission creep is contractor driven. "
I would say mission creep is stakeholder driven - broader than just the contractors. Scale and funding = power, so the gov agents gain power with scope.
But more frightening is that Knowledge = power.
J. E. Hoover learned early that everyone has hidden skeletons of one form or another. So this massive effort for "Total Information Awareness" has taken over the goal of lining one's own pockets with the scraps from IT contracts, to having total leverage over any person or group through complete 360 degree knowledge of everyone - their thoughts, actions, and associations (even types of associations and details of transactions).
Absolutely the top NSA bureaucrats want to build a larger bureaucrat empire. They become more powerful this way....But this also translates into money. A top NSA job also makes them more desirable to hire after they retire or during a respite form working for the USG. So means they make oodles of money as compensation for steering various contracts to contractors X and Y by getting very cushy jobs at X or Y. They will then labor at X or Y to lobby their NSA friends (past co-workers) to secure more NSA contracts for contractor X or Y
There is a lucrative revolving door of employment between NSA and its contractors