I’ve been out of the Power Industry/SCADA game for about 6 years now, and never had huge involvement with solar farms, so please take this with a large grain of salt, but here is my take. 15 years ago, all anyone would say about industrial networks was “air gap!”. Security within SCADA products was designed solely to prevent bad operators from doing bad things. Security on devices was essentially non-existent, and firmware could often be updated via the same connectivity that the SCADA system had to the devices (although SCADA rarely supported this; it was still possible). In addition, SCADA systems completely trusted communication coming back from the devices themselves, making it relatively simple for a rogue device to exploit a buffer overrun in the SCADA. After Stuxnet + a significant push from the US government, SCADA systems moved from “defensive boundary, trust internally” to “zero trust”. However, devices have a long, long service life. Typically they would be deployed and left alone for 10+ years, and generally had little to no security. Security researches left this space alone, because the cost of entry was too high, but anytime they did investigate a device, there were always trivial exploits.
Although SCADA (and other industrial control software), will be run on an isolated network, it will still be bridged in multiple places. This is in order to get data out of the system, but also to get data into the system (via devices, and off-site optimisation software). The other trend that happened over time was to centralize operations in order to have fewer operators controlling multiple sites. That means that compromising one network gives you access to a lot of real world hardware.
Engineers never trusted SCADA (wisely), and all of these systems would be well built with multiple fail-safes and redundancies and so on. However, if I were to be a state-actor, I’d target the SCADA. If you compromise that system, you have direct access to all devices and can potentially modify the firmware to do whatever you want. If there is security, the SCADA will be authorized.
I don’t think the security risks are overblown (they are overblown in what they think the real problems are). I think that as the systems have gotten ever more complex; we have such complicated interdependencies that it is impossible to deterministically analyse them completely. The “Northeast blackout of 2003” (where a SCADA bug lead to a cascade failure), was used as a case-study in this industry for many years, but if anything, I think the potential for intentional destruction is much higher.
