They paid devs and gave them Lumia phones. I still remember writing a trivial app for Windows Phone and getting $100 and a Lumia 521, which was pretty good IMO.

Google acted terribly towards Windows Phone, breaking Youtube and anything else 3rd party devs or Microsoft wrote for Windows Phone. Google Maps for mobile browsers was pretty awful until Google was sure that AT&T and Verizon were done selling Windows Phones

Google's actions were still anticompetitive even if Microsoft's effort would've fallen apart on its own.