What benefit does Microsoft have by using Mozilla instead? Earnest question.
Electron, the software framework VSCode uses, runs on Chromium. Github maintained and developed the framework and they are currently owned by Microsoft. If Microsoft contributes to Chromium and improves performance they benefit in a lot of places: their new browser is improved(Edge Chromium), their own framework(Electron), and their own product (VSCode).
They aren't really dependent on Google with Blink, though. They have developer resources that can maintain a fork of it. If Google does something Microsoft doesn't like they can just remove it form their tree or implement an alternative of their own design.
They can diverge from Chromium around the edges but they are dependent on Google for long-term Blink evolution. That includes not just the internals but also APIs. E.g. if/when Google removes powerful content-blocking APIs from Chromium, Microsoft is would struggle to maintain their own different API. Especially for APIs that have architectural implications ... converting something from sync to async or vice versa. Significant architectural divergence would get expensive pretty fast.
Then again, they would face the same issues had they adopted Gecko. Maybe less so because Mozilla could be more easily influenced than Google (in some ways). The main argument for adopting Gecko would have been that giving Google complete control over Web evolution is a threat to Microsoft and that adopting Gecko would reduce that threat. I'm a big Mozilla fan but I think it would have been a weak argument.
Huawei depended on the proprietary bits of Android ("Google Play Services"?). In contrast, Microsoft is knowledgeable enough to use only the permissively-licensed parts of Chrome as the point of departure for their fork.
Also, if Huawei were to fork Android they'd be responsible keeping their fork of a huge code base secure by push security updates, and Microsoft is much more likely to be able to do that competently than Huawei is.
Electron, the software framework VSCode uses, runs on Chromium. Github maintained and developed the framework and they are currently owned by Microsoft. If Microsoft contributes to Chromium and improves performance they benefit in a lot of places: their new browser is improved(Edge Chromium), their own framework(Electron), and their own product (VSCode).