Threatened them with what? They don't seem afraid to go after Google (cf. Bing), nor should they.
It's a shame the feature you're describing hasn't been released, really! Any hope it might? When was this?
Microsoft and Google each have subtle and not-subtle ways of attacking each other. Google doesn't really feel threatened by Bing, everyone thinks Bing is a joke (even if it is pretty decent), plus Google steals all their best ideas from Bing. But things like the popups Google has on their sites to tell Edge users Chrome is better, Microsoft's retaliatory popups in Windows that tell Chrome users to try Edge, etc. Google has aggressively broken compatibility of their various services with Windows Mobile devices before. They definitely have options if they want to harass the others' customers.
Microsoft already HAS developed the ability for Windows Phones to run Android apps. (They actually sent me a free phone just to test the feature!) Sadly, they decided not to release it, and we don't really know why. It could have been that they were worried about developers settling for Android apps instead of making UWP apps. Or Google could've threatened them, which seems plausible too. (Android is kinda "open" source, where yes, it's open source, but Google will do underhanded things if you dare to use it in any way they consider a risk to their dominance.) I can tell you the Android Bridge for Windows Phone worked amazingly, and my demo unit phone still has that version of Windows on it.