I don't see why this would make anyone thinks this is illegal as it doesn't stop anyone from buying Google Home products. It isn't as though Best Buy is selling Amazon products and Apple stopped selling nest in their retail stores as well.

At this point, Alexa works nicely with my Nest thermostat. If they break that, then I will be mighty annoyed because I will have to reach into my pocket to change the temperature instead of just blurting out the desired temperature of my abode.