I think it's a combination of all 3 reasons you listed. Overall people have realized that all they need is internet connectivity and a browser for 90%+ of their use cases. That remaining 10% is growing smaller by the year as applications move to the cloud rather than run locally - or can probably find a similar Linux app.
Another big selling point is that Chrome OS supports Android apps, e.g. you can download Netflix shows to watch offline, or just use the same apps that you have on your phone. This might be the dark horse as Windows ARM apps support is pathetic and MacOS now also supports running iOS apps.
That said I'm also skeptical on the prices for Chromebooks - for a similar spec-ed laptop, Chromebooks are strangely a bit more expensive than a Windows counterpart.
Don't be condescending. I'm as sophisticated as any computer user has ever been and my Pixelbook Go is my daily driver, not the laptop I bought for my mom. It's just better in ways that matter. No fan. Epic battery life. Software updates in 2 seconds, not 2 hours. Wakes so fast that it's up and running and on wifi before the lid is even open. Has a terminal and an X11 server and a web browser, the only things I require. Survives being attached to external monitors and audio devices. Does not have useless little software buttons above the keyboard. Better touchpad gesture detection than even a Mac. Can powerwash it in 1 second if I ever want to sell it.
The built in Linux environment (Crostini) is more or less vanilla Debian, and is extremely easy to install. Want to use Firefox, or VSCode, or GIMP? Trivially done, and integrates seamlessly with the rest of ChromeOS.
Yes, the $200 devices are not as good as $1000+ laptops, but for the price, I think they are pretty great. I use one for both personal and work stuff (not as a primary machine, but for travel and field work).
Have a brand new Pixelbook Go i5-16gb and as I lurk on HN to try to find some light about my purchase and whether I made the right move; I just found that light!
Bought my chromebook three years ago and it was rock solid until about a year ago when suddenly the updates became irritatingly unstable. The bluetooth mouse stopped working. Wouldn't recover from sleep properly, among other stuff. Seems to be working just at the moment but I feel like I'm walking on egg shells every time there's an OS update.
* Schools: School laptops were already a thing, I don't see how pandemic can significantly change those numbers.
* Price: Chromebooks are now much more expensive. And there are more cheap windows laptops now.
* Ease of use: Maybe this is tech savvy people buying laptops for their grandparents so they can keep in touch?
I don't know the answer. But as much as I hate recommending google products, chromeos is now a really good option for a lot of people.