Yes, mshtml was insanely powerful. As an undergrad I was surprised how easy it was to build capable UIs with powerful visual effects[1] using mshtml and JS. Even for C++ Windows apps.
It took a long time for this to become a cross-platform reality, but it did inspire me to ignore distractions like XAML and focus on the web.
This was already a thing 20 years ago. Students weren’t have any experience with windows, it was something companies used, and today even that has gone away.
Windows is still enforced and mandated on most corporate Fortune 100/500 companies computers.
Their "cloud lift" consists of putting vms into the cloud to run at 10x the cost. (Nothing else changed from The Old Ways)
And that's still where we are today for most enterprises.
That ecosystem has had them for 30+ years and shows no signs of going away anytime soon. If it doesn't have Active Directory and Office 365 or whatever they decided to call it today, they aren't interested.
Windows 98 introduced Active Desktop, and still, not as many webviews all over the place.
MSHTML was the first Electron.