Microsoft can easily act as Google's counter balance. Microsoft is one of the few companies that have the resources capable of maintaining a hostile fork of chromium (at a loss) and have it competitive enough that users will switch. Google has lost it's one advantage in the web-space too as now they can't exactly hamper the experience of edge without hampering chrome too.
Chromium needed this counter-balance.
If Microsoft chose a Gecko forked browser, they would dominate and take over. Like what Apple did with KHTML. This step is better.