On the contrary, it’s the whole ballgame in a case like this. Google’s claim will be: “we have high market share because our product is good. Look - customers could switch for free if they didn’t like it.” The government cannot make a monopolization claim solely on the basis of high market share in this case. It’s not remotely persuasive. (Indeed: who do you do your searches with??)
>> “there is evidence…”
Totally agree with this sentence. But it’s not going to be decisive for the government. It will not be remotely sufficient. Again - it’s not clear to me personally that this behavior is pro-competitive. But I’ve already told you what google is going to say. If you’re going to argue monopolization you have to define the market (here search) and then show it’s monopolized. Market share isn’t enough.
>> could see it more as collusion…
Not legally. Sorry. Not without some specific evidence of a conspiracy.