Microsoft’s as network isn’t really relevant nor a significant driver of business decisions at Microsoft. Disclaimer: former FTE SE, and I worked on Internet Explorer briefly in 2015.
Chromium-Edge was forked after I left MS, but from what I gathered the higher-ups were aware of how far-behind MSHTML+EdgeHTML was, and it was getting worse with each Chrome release. One major problem was the rise in the popularity of NodeJS and Electron: both of which trounced Windows’ Chakra engine and legacy HTA platform (and no-one was building for “Windows Store HTML” for obvious reasons), especially on ARM (IIRC, Chakra didn’t JIT on ARM).
Anyway, Microsoft’s problem is they don’t want to lose the web to Google because they recognise the web is now “the platform”, including desktop “web” apps running in Electron. Any business knows it’s a liability to have dependencies on your competitors. The plan, originally, was to base Edge on Chromium, then built it into the OS, so desktop apps can use modern Chromium features in a build optimised for Windows and the user’s computer without needing 200MB+ Electron packages and 400MB RAM and dozens of separate processes for what should be a trusted application.
...however that still hasn’t panned-out yet. Which I find concerning because I thought Microsoft would treat Chromium the way Apple treats Safari: a browser that puts the user - and their privacy - first, because Microsoft isn’t Google and doesn’t significantly benefit from tracking users over the web.
...but they have been. Edge’s privacy stats are almost as bad as Chrome’s. I’m guessing some GP or VP from the Bing org had a word with OSG’s VPs and convinced them to compromise Edge to benefit Bing despite the overall damage to the Microsoft brand and eliminating possibly the most important advantage Edge had over Chrome.