Well, it's kind of explicable: It was at about that time Microsoft rolled out HTML Help, so they needed an HTML rendering engine on every PC to be able to read the documentation.
Using a web browser as your native app's rendering engine is what all the cool kids are doing these days, so in a way they were just 15 years ahead of the curve.
As others have said parts of explorer were using mshtml for the user interface. However it wasn't just Microsoft. Third party vendors used mshtml as a component to render their UI! You can find samples around still, e.g . https://www.codeproject.com/Articles/6845/Implementing-snap-...
Most memorably, Norton Antivirus 2003 (I think) was one such application. The entire UI was in fact written in HTML with lots of callbacks into c++ code.
So in many ways... Electron isn't all that new of an idea :)
[Edit: I'm actually thinking of the EU lawsuit that was probably broader and better managed than the US one. Memories are now vague, it took me a while to even remember US and EU had different suits, but sure th US one was a lot worse in many aspects as Microsoft was on their home turf.]
> every MS competitor just did what MS did and didn't get smacked for
If you believe this, is the fault on those who smacked MS or the regulators who didn't smack the later violations ?
Is your argument that a crime shouldn't be punished in the past if people fail to punish it later in the future ?
Not precisely, but I do believe punishing one corporation and then not punishing their competition starts to smell a lot like using the force of the law to create an unfair market disadvantage.