Basically because the current philosophy of the US justice department anti trust prosecutions is whether market dominance of the player harms ordinary people or causes them to incur higher cost. It is not really about actual monopoly power. Google has been pretty careful to stay consistent with this philosophy.
This wasn't always so in the US and it's not the same philosophy in EU. However, it is a valid and consistent view.
Counterpoint: If you strongly want your government to change its approach, organize to change the government.
In US, it's very safe to do this without violence but even in significantly less safe places, people have successfully done this peacefully [1] [2] [3]
This wasn't always so in the US and it's not the same philosophy in EU. However, it is a valid and consistent view.