Sounds looks a solved problem, but it isn’t. The electrical grid isolates SCADA networks from the internet, so substations are interconnected via dedicated networks. But then at the command centers you have the entire monitoring and control systems with on site operators. Then, inevitably you will have some employees with vpn access, and now you have 2 vectors: remote admins getting hacked and local admins plugging in external devices. You’d think it’s easy to get rid of vpns, but things like the pandemic brought them all back to full force.