Regulation is the worst solution to any of this. Let the free market figure it out and you'll find enough competition if there really is enough demand.
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.
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.