Punishing companies for producing a wildly successful product is a strategy that will result in competitive choice between multiple sub-par products. Strategically that seems kinda dumb.
The question of Google negotiating for default search engine status is just not a big enough problem for regulators to be involved. If the legislators want to ban that as something corporations can do then I suppose that is there prerogative, but the "damage" here to anyone that matters is hard to spot and it remains a bad idea to pile-in on Google. And the legality of preferred search engine arrangements shouldn't hinge on if the product is popular or not. How could it help anyone to ban them only if the product is the best on the market?