The story of it is interesting: Clifford Cocks was working on it, he went home, and had the realisation at home. He could not write it down because that's not what mathematician spies do, so he had to remember it overnight u til he went back to the office the next morning.

Want to consult with person X who is trusted by authority Y to do Z at a level L? This is straightforward without a bespoke who-trusts-whom website (heck, it's possible without "users") if we have PKI.

Every year we don't have PKI is quite possibly trillions lost globally. If the NSA has been the one preventing the adoption of widespread PKI, then this is the cost they have imposed.