Anti-trust laws, for example. Safety and environmental regulations.

Yes. In some sort of ideal world, where corporations would never dream of regulatory capture, abusing a monopoly position, finding ways to keep upstarts out of the way.

In the real world, capitalism is an unstable system. The "winner" gets too close to the state and then tries to shape the rules so they fit the incumbent and discourages everyone else. Boeing and the FAA is a recent high profile example.