Why would a tech company not build its flagship product natively on the platforms where it runs? It seems like a generation drift: an obliviousness to the world outside of JS/web dev, and a general disregard for application performance.
Hell, if you're not afraid of bloating in the codebase, you could use a large number of libraries to put together a basic, working version inside of a day or two. Stretch that to a couple of weeks (at most) and you have a prototype you can release.
The proof is in Atlassian and Microsoft chasing after Slack on this. Very few people came forward to wave the "Let's just go back to IRC" flag.
It's shiny, new, you can drag and drop gifs and files into it, and it runs pretty swiftly (ignoring all of the obvious flaws). Most, especially less technical, users would find it a charm to work with. In my experience, they do -- and above all of the competitors.
The rest of your points are rather valid. But maybe its not so much obliviousness, as eagerness and impatience, and the reality of the market being as timely and pressing as it currently is. It's a race -- just like the telephone and the radio (for my point I'm ignoring the scale of impact here).
That's the problem right there(?). People bringing a DOM to the desktop because the developers were fluent in JS.
> time to market
If there were no drawbacks in terms of complexity/performance/size etc then I'd agree, but now when you have a perf issue that is too large it might be a huge issue to fix. You also only get one chance for a first impression - and poor performance is a huge turnoff. Looking blingy and having all the features doesn't save an app with a 200ms lockup. or a 10% CPU at idle.
I saw this happen at work. My team were all experts on native mobile development. We could crank out stuff fast, because we knew our tools well. But then some management dude got the idea that we would do it 2-3x faster if we went with JavaScript.
Turns out it was more like 2-3 slower than making all the native versions, because we did not have strong experience with these tools and APIs were more limited, poorely documented, buggy, and the tools were subpar.
Given that constraint, time to market becomes crucial as the huge cross platform barrier is significantly reduced by Electron.
It's also a demographic shift. Young developer's aren't coding in Java peak world anymore. We haven't even reached peak Javascript yet.