Earlier quoted context omitted.
Really it was the Chrome v8 engine paving the way for electron and Single Page Applications.
It's not because of V8. It's because HTML+CSS (without even any JavaScript) is still the fastest, most effective way to build a compelling and coherent UX/UI for any platform right now. WPF (nee Avalon) was a contender in the mid-2000s, but for some reason Microsoft put it on ice by 2007 leaving the community stuck with incredibly verbose and bloated XAML markup which only made development more tedious than WinForms,…
I would agree if you mean cross-platform, but other than for the web specifically, basically every platform has a much better way to create an app for it. The web is seriously so lacking on several trivial fronts that it is laughable, layouting being one example, but just creating a slightly modified version of a native widget like calendar require the recreation of the whole thing with quite bad primitives while goddamn WinForms could deal with it through inheritence.