There is bureaucratic fight between the NSA and the White House (DHS is a cabinet position) over who gets unfettered access to ALL government networks in the guise of security.
The stories of power grid and SCADA control breaches, the F-35 leaks and nameless Chinese hackers are FUD originating from the NSA to scare other government entities into surrendering full control of their networks to the NSA.
In his resignation letter he states that " NSA effectively controls DHS cyber efforts through detailees, technology insertions, and the proposed move of NPPD and the NCSC to a Fort Meade NSA facility. NSA currently dominates most national cyber efforts. While acknowledging the critical importance of NSA to our intelligence efforts, I believe this is a bad strategy on multiple grounds. The intelligence culture is very different than a network operations or security culture. In addition, the threats to our democratic processes are significant if all top level government network security and monitoring are handled by any one organization (either directly or indirectly). During my term as Director we have been unwilling to subjugate the NCSC underneath the NSA. Instead, we advocated a model where there is a credible civilian government cyber security capability which interfaces with, but is not controlled by, the NSA. "