Why do you assume that this was done not at the direct orders of the executive branch?
The director of the NSA is a general, the NSA is the only intelligence agency that is almost under the direct control of POTUS.
The difference is that we elected the guy doing the overseeing, Barack Obama. In fact we elected him twice. That's democracy. If we don't like what NSA is doing under the President's command, we'll elect a different president, or our elected men and women in Congress can hold the President accountable.
> If we don't like what NSA is doing under the President's command, [...]
For that, you would need oversight, which intel shops typically don't provide. For instance, there's a history of scandals being revealed long after they were done in western democracies.
There's also the matter of being able to effectively implement a political program reducing the powers of intel agencies. To my knowledge this has never happened outside of political upheavals. Even then, if you look at the Church committee report and the Snowden affair, advances seem to be quickly erased.
Remember when the CIA managed to finally get even Feinstein to make statements critical about surveillance, after it was clear that the CIA was caught spying on the Senate intelligence committee while they prepared the report on torture?
Snowden is another good example of how poor the oversight is - whether because they didn't think any of what has been revealed was wrong, or because they didn't know. I'm not sure which is worse.
What's the difference between an unelected man in charge and an elected one, if you can't know what they do, anyway ?