This assumes that starting up a competitor is frictionless and has zero-overhead. If the market which is now dominated has a large enough barrier to entry the m

This assumes that starting up a competitor is frictionless and has zero-overhead. If the market which is now dominated has a large enough barrier to entry the monopoly can temporarily return to their loss-making tactics to starve you out. Capital will rightly look at your business and ask why they should invest in it when they can just get onboard with the current monopoly and get those profits instead. There's a reason that we had to deal with monopolies largely through regulatory means, and it's not because we were afraid of letting the market correct itself, it's because, by and large, the market does not correct itself once a stable monopoly has been erected.