It's his attempt to damage the investigation and give Trump cover. It's another diversion.
Anyone who follows this space knows that the NSA surveils all sorts of stuff as a normal matter.
He didn't tell Schiff because he knew it was trivial. He's harming the investigation by trying to undermine the veracity of the intelligence services.
It's all deliberate. Trump may use this to fire the intelligence chiefs and replace them with his stooges. The coup expands.