You discount the abilities of monopolists to prevent new market entrants. They can lower prices only when there is a new player, until that player goes bankrupt, and then raise them again, discouraging others from trying again. They can lock up suppliers in exclusive contracts, preventing competition from sourcing parts. They can run massive disinformation campaigns. They can launch a series of baseless lawsuits. Etc... It's straightforward to have an abusive hold on a market without any government involvement at all, all you need is some deviousness.