the internet in general kind of sucks these days. Reddit has burned down a lot of the things that made its search results so useful in the past. Every forum post more than a few years old is a forest of broken links; the top of basically any internet search whatsoever is an ocean of SEO spam. And that’s before you get into the sheer amount of information that isn’t searcheable at all because it’s on platforms like discord.
Yep, this is it. I volunteered for my school’s IT department in high school, this was basically the logic. The laptops are cheap and easy to manage/administrate. Whether or not they were Linux was a non-issue.
Edit: also, since chromeOS is basically just a browser, there wasn’t much that could break, and if something did break everything was stored in google drive anyway, so you could just factory reset the device and hand it back to the student without needing to buy any kind of higher-level support contract.