This article kind of misses the forest for the trees. While I agree with many of the author's points, that's not why the #TwitterMigration failed. It failed because Twitter/Mastodon isn't really a social networking site, and Mastodon didn't provide the same service that Twitter does. At its core, Twitter is about small numbers of (usually famous or important) users communicating with large audiences of followers. #TwitterMigration failed because not enough of those famous and important people moved from Twitter to Mastodon, so the average user had no content they cared to read. Seeing posts from your friends about what they had for dinner last night is all well and good, but the stuff people actually want to see is famous person A throwing shade at famous person B while famous person C talks about the new movie they're in and important organization D posts a warning about severe weather in the area. You don't go to Twitter to have discussions, you go to Twitter to get news and gossip direct from the source.
In contrast, sites like Reddit and kBin/Lemmy are about having group conversations around a topic. Interacting with famous people is neat but not the point. Think of Reddit/kBin/Lemmy as random conversations at a party whereas Twitter/Mastodon is some random person on the corner shouting to a crowd from a soapbox. #RedditMigration has a much better chance of succeeding simply because the purpose of the site is different. As long as enough people move to kBin/Lemmy to have meaningful conversations (aka content), it will have succeeded.
That's a click-baity headline that doesn't really match the content of the article. Microsoft isn't going to be replacing desktop Windows installations with cloud installations, and nowhere in the article does it suggest it is. Many, many businesses require Windows installed on the desktop (and no, many of those can't switch to Linux, because the software they use is usually Windows-only). The article doesn't dig into who is currently using Windows 365 to stream the OS, but I would assume it's companies that are running computer kiosks, point-of-sale systems, or systems that would otherwise be extremely locked-down (like bank teller systems). Businesses that need system flexibility and resource-intensive applications aren't going to be using a cloud-based OS. Pretty-much any business that does engineering or creative work falls into that bucket.
My interpretation of the article is that they want to extend cloud-based Windows to other users that have extremely lightweight requirements. The biggest market I see is the education market, where you generally want to provide students with very locked down functionality. The article mentions competition with Chromebooks, which is also huge in the education space. I could see this as a competitor to an iPad/tablet too, for those who mostly do browsing, email, or lightweight web-based MS Office tasks and want to have a keyboard and mouse.
TL;DR: People are wildly misinterpreting this article, and there isn't going to be any kind of mass exodus to Linux because of Microsoft investing in Windows 365. Microsoft isn't going to stop selling installable copies of Windows.