in a free country you think you would be able to sue for copyright infringement on uploaded content, but section 230 protects platforms from this to some degree.
the idea is since they benefit from this huge government-granted privilege/protection, maybe users should have the same free speech protections citizens have via the first amendment in this particular case.
I am not a lawyer or that into politics, so I don't have a strong opinion on this, it's just an argument that I heard from a commentator.