I'm curious what you base that on. For instance, we've never really allowed literally cutthoat competition, nor things like fraud and we've generally not allowed misrepresentation. Governments intervene heavily and always have to set those kind of boundary conditions - but there are really lots of them. Economies of scale seem to be very, very common ever since the industrial revolution; and even more so in today's information-economy platform era.

I'm sure there are plenty of cases where significant competition is a natural end state, but how common those are in comparison? I'm curious.

The observation that the least regulated markets are typically the most competitive ones and that large companies rarely tend to maintain their lead over long periods of time. And at least one Nobel Prize-winning economist agrees with me: https://www.youtube.com/watch?v=tdLBzfFGFQU

While a humorous response by Milton and an interesting debating point, the argument he makes is pretty weak because it almost inevitably reduces to complete lawlessness, doesn't really define which government "granted" monopolies he's willing to give up, and ultimately relies on a fairly arbitrary definition of what government even is - and one that if you really let it go to the extreme not only obviously just doesn't work well for most people, it also does not avoid monopolies as is witnessed every day around the globe.

After all, the natural inclination of a powerful elite is to protect their interest. It's business 101 to want a moat, and tearing down one set of artifical legal protections that allows for a moat allows on the other hand for the far more extreme quite physically violent moat in the form of a putin-esque kleptocracy.

The argument merely sounds convincing because it's very selectively implying that certain monopolies are created by state power and might be weakened by free market principles without considering what a free market even is (generally a regulated one), nor addressing the fact that other monopolies will arise precisely because because the lack of regulation allows winner-take-all brute force strategies to work.

That doesn't mean Milton's ideas are without merit - but that there is a breaking point; dogmatically hoping for anarchy to avoid harmful centralization of power is problematic because of the dogma; not because it's never a valid approach.

But sure, if you're going to embrace Milton's (intentionally) vague proposition in the way it was likely intended - to provoke thought - then sure; there are state regulations that are in part to blame for some of today's near monopolies - the interaction between intellectual property, incorporation, and state-enforced contract law. As a matter of debate, sure, it'd be interesting to weaken all three and in particular their interactions. I just highly doubt that's very practical, nor would it be very easy to predict the outcome, especially once international power-plays start circumventing even the best of intentions.