The "free market" will always, always end up with large fish eating up the small fish and extracting rents once the competition is eliminated and the startup costs too high for startups to enter the market.
I still think this has much more to do with market interventions enabling 'artificially' large economies of scale. Infrastructure, police, subsidies/grants, IP protections--all played and continue to play a massive role in shaping markets today.
Regulation, on the other hand, does tend to lead to rent seeking behavior as incumbents use those laws to their advantage and forcibly block new companies.
It’s much easier to overcome high costs than bad laws.
And that's only because of current regulations and anti-competition laws. Turns out "free market" is only "free" when the giants are asked to behave and punished for bad behaviours.