Who will stop Google and other Oligopolists?

USA certainly will not, they are an extended arm to preserve control over the other economies and states. Google reaps huge benefits from being able to exploit its near-monopoly on search, use of personal data. EU completely passive, as are individual member states. Only way to stop Google, Facebook, Apple, Amazon is Direct Democracy.
How Google's parent company is paving the way to become a transportation giant

Facebook to double (Political?) 'Safety and Security Staff'

And there are already 10,000 staff toiling in this department - fine line divides it from (private) censorship. The future does look Orwellian! And who controls Facebook? It is an oligopoly! Who controls what you are 'fed' (yes, we are basically like animals for the 'Masters of the Universe' controlling the Web).
CNBC

Facebook meddling with Media Content

It is about time that the dominating Internet Portals such as Facebook and Google are brought under democratic control. When providers have a dominant market share the Competition and Monopolies regulators should not be fobbed off with spurious arguments such as 'we must not interfere with new technologies, ie stand in the way of progress etc'. What applied to Rockefeller's Standard Oil in the early 1900s must apply to the Internet Barons today. When the providers start tinkering with the flow of news and information alarm bells should start ringing in the sleepy offices of the regulators and legislative assemblies. Naturally, the USA will not be too keen as most providers are based there but a confrontation with the lobby-infested corridors of power in Washington can not longer be avoided.

Facebook cracks down on clickbait