You challenge that it is stiff competition in your first sentence, then you define that Google is, indeed, stiff competition in your second.
Hijacking search results because they are sour the Yelp deal didn't go their way isn't competing LOL. They've already been fined billions for similar behavior.
They own the search results. Google isn't a public utility that gets hijacked.
Yelp can start their own search competitor if they enjoy(ed) the synergy.