That's wrong. You are assuming a barrier to entry for a new competitor that is higher than the future profits for entering the market. Sometimes that exists (

That's wrong. You are assuming a barrier to entry for a new competitor that is higher than the future profits for entering the market. Sometimes that exists (Google search?), but sometimes it doesn't. As a thought exercise, imagine WeWork drove every office rental company out of business in the United States by running at a loss. To make a profit, they would have to raise their rents. When they do, any company can re-enter the market by buying or building office space to compete with them.