When Microsoft beat Netscape with IE, it was by building a far better browser. Google is a stronger competitor than Netscape ever was though. Without Google dropping the ball (like Netscape), Microsoft would never exceed Chrome's performance by enough to be the fastest, most compatible (with Chrome), etc.
It is also just classic Microsoft when they are hungry. Like making Word use WordPerfect files and keyboard shortcuts. Only today it is that their browser is mostly Google, Linux is built into Windows 11, SQL Server ships on Linux, and their most popular IDE is open-source built on open tech (Electron) they didn't create.
When they get threatened, nothing is too sacred for Microsoft to kill or adopt.
Microsoft firing on all cylinders, when they want to, is a terrifying force.
Just like management doesn't a F about the state of UWP, WinUI and anything related to it.
Microsoft lands many changes in Chromium first before they show up in Edge (logistically it's easier to do things this way for merging reasons), but they do also upstream changes to Chromium that show up in Edge first.
I haven't trudged through Chromium's commit statistics but has Microsoft been upstreaming many contributions? I'm skeptical that they are ready to take on the full brunt of Chromium maintenance on a whim, it would take a decent while to build up the teams and expertise for it.