It was the SCADA view right? A lot of SCADA software is basically running on top of windows, though you typically would never see the desktop. Ignition at least is cross platform, but that is because the server is Java and Jython. A big part of why things are running on windows is due to OPC, which was traditionally all DOM and .NET. It is basically a standard communications protocol and is what allows your HMI/SCADA to communicate with PLCs. Otherwise, you use proprietary drivers and native PLC specific protocols.

SCADA programming/design is kind of an art and is usually written by an either an overworked engineer or someone who had far too much time on their hands. You basically build screens using specialized software, hook up buttons and UI elements to PLC signals, and pass some signals from the UI to the PLC. They are all heading in the Edge/iot/cloud/web based/techno-babble direction these days...

Ignition, programming software is free!: https://inductiveautomation.com

Some other random ones I have seen or used in the past: https://www.siemens.com/global/en/products/automation/simatic-hmi/wincc-unified.html https://www.aveva.com/en/products/intouch-hmi/ https://www.rockwellautomation.com/en-us/products/software/factorytalk/operationsuite/view.html