This just means, “people shouldn’t be able to own large companies”. You’re going to need strong evidence that relinquishing ownership of any successful company to the government (or whoever you give the absconded shares to) is a way to run a sustainable company.
What large country (50m+) has successfully eliminated billionaires without eliminating most of their own economy?
Why the government? Why not collective ownership by workers, and maybe partly to users in applicable cases?
Also, why would the existence of such big companies be an absolute necessity in the first place?
Big orgs (regardless of public or private) can exploit economies of scale, which makes cheap products possible and available to the masses.
Big orgs have big org problems that small orgs don’t (HR, Legal, Architecture, …), so they need specialist senior leaders who spend their days doing things that rank-and-file staff don’t understand, and usually don’t even know need to be done.
HN loves to rag on the C-suite, but they are real jobs that need real skills. To all the armchair CxOs confident that boards are idiots and are paying their execs for nothing, all I can say is: try it.
And the problem with large corporate boards isn't that they're idiots - it's that they're dominated by sociopaths. They aren't paying their execs for nothing - they're paying their execs to screw over their employees and their customers most effectively - which is, indeed, a real job that does need real skills.