Honestly, it’s not as difficult as you might think. People have been using codes and cyphers as long as there has been writing and probably much before then. Explaining the need to keep things secret while communicating to people who are modern enough to have radio? Pretty easy.
Explaining why things connect to the internet and then get compromised by foreign attackers?
Hard. People would be like “why would you connect to the same system as Russia”
For the same reason that everyone used the Knights Templar or Venetian bankers to pass messages and money.
EDIT: And you’re talking only 100 years ago. We had radios, telegraphs and telephones 100 years ago. It was reasonably common knowledge that it was possible to listen in on those even if you weren’t the intended recipient. Heck, part of the plot of The Count of Monte Cristo (1846) involves hacking a telegraph system with a MIM attack to manipulate international financial markets.
You do realize that we’re not, right? There are private lines that run for secure communication.
I wish
The thing is people want easy and air gapping the system is not easy.
