Free markets self-regulate, but that actually doesn't describe their possible outcomes. This could be an outcome.
Discussion
It could be, as could a monopoly, it's just that in freer markets, stuff like this is less likely to happen.
Why?
Most of modern monopolies are created or strongly supported by regulations and state enforced the rules.
They create artificial barriers for marker entry/competition.
Yes. After them being created by the lack of regulations. Regulations ate important, that's why they create these barriers to avoid competition etc
They don't self regulate, see above...