Google already has good AI researchers working for them and have similar AI models, but Microsoft is much freer to act in this space. they have hardly any reputation in search so any crazy stunt they pull will be good PR for them. any crazy stunt Google pulls will be bad PR for Google.
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no one takes Bing seriously so Microsoft has nothing to lose and everything to gain by disrupting the search space.
if you've been following what Microsoft has been doing in the software development space since Bill Gates left, you'll see that their approach has radically changed.