Oligopolies are unlikely in a free market because as soon as you do anything interesting a million other people will copy what you are doing wholesale and you will have no advantage to see you rise up to form an oligopoly. We find oligopolies in our regulated markets because regulation, such as copyright, patents, tariffs, etc., legally hinder that competition from emerging.

However, even if we accept oligopolies as inevitable, that doesn't mean the tech people cannot collectively own those oligopolies. A business does not have to be owned by just one person. Cooperatives are a thing.