It's hilarious that the most liberal companies on Earth like Google or Facebook are so often accused of promoting "right wing" ideas too much, when they very clearly do everything in their power to censor right wing people at every turn.
If Google was split into four companies with three or four viable competitors, might not those new competitive marketplaces contain some companies that conservatives prefer, some that liberals prefer?
If Instagram was a separate site from Facebook, might they not organically develop different internal policies to encourage new customers to choose them over competitors?
Accepting your premise Google "so clearly do everything in their power to censor right wing people at every turn", would not creating a market for Google-provided services be the most market-driven way to explore alternatives?
The only alternatives I see are "Communism of the Media", with extra steps.
Also, just spitballing here, but in a world where Left and Right agree that bigness is bad, we can write new laws prohibiting should the existing ones prove insufficient in practice.
Crazy!