Edge isn't doing so well: Chrome still rules the web roost, and Firefox is resurgent. But Microsoft can do something about that.
Companies like Google or Microsoft have used their market position in the past to push their own products. Google pushes Chrome on all of its properties when users use different browsers to connect to them, and Microsoft too displayed notifications on the Windows 10 platform to users who used other browsers that Edge was more secure or power friendly.
The intercepting of installers on Windows is a new low, however. A user who initiates the installation of a browser does so on purpose.
The popup explicitly describes itself as a warning—as if intercepting malware. 2018's Microsoft, same as 1998's Microsoft.