It's disheartening that data diodes aren't widely deployed to allow for monitoring of critical infrastructure while making ingress of control (and thus hacking)

It's disheartening that data diodes aren't widely deployed to allow for monitoring of critical infrastructure while making ingress of control (and thus hacking) physically impossible. We've known how to do this stuff securely forever, yet here we are. My personal theory of how we got here is thus: in the late 1970s, it was decided not to push the recent advances in capability based security out to the wider world, as it would make the NSA's job just a bit harder.