"Fully free market" in modern economic speak is pressing for laissez-faire policies (except of course for leaving security of property to the government -- a truly fully free market would have security market based as well).
You're talking about open markets with free participants who all have equal access to markets and even information about markets. That is often called "open markets" in the 21st Century.
I never said "fully free market" in the sense of government non-regulation. I'm talking about "fully-free markets" with fair trading practices. Unfortunately, the larger an actor, the more ruthless they become.
I gave one example:
The robber barons of the 1880s. In particular, the railroaders.
A local restaurant has been around for decades, owned by some old mom and pop. The railroad comes to town, which benefits said restaurant. Until it doesn't, as the railroader decides they will open their own restaurant right next door. Seeing as they have such a huge flow of cash behind them, they can afford to break the local free market economy by purposely dropping prices to rock-bottom and purposely lose money in the venture just to put the mom-and-pop out of business. Just because. The railroad monopoly doesn't NEED a restaurant. It isn't going to really affect their bottom line. They could just easily shut down that restaurant a week after they put the mom and pop out of business. They could decide the entire venture wasn't really worth their time and effort after all.
But it DOES greatly negatively affect the owner of the dead business, their employees, and their supply chain businesses; presumably local farmers and dishware makers. It also resonates through the local culture of the town. One less popular hangout. One less businesses for travellers to spend money in the town.
That's not how a free, open, and natural market is supposed to work. The Progressives of that time period recognized this. The Progressive movement grew and grew, as a huge majority of people from every political spectrum understood the urgency the situation. For a time, up until the campaign and election of 1912, every party had a progressive platform.
The economic and manufacturing output of the USA was nothing short of a miracle under the rules and regulations that allow as fair trading practices as possible, in order to get as many people from as many backgrounds as possible to be able to participate. The more that participate, the better the information for all involved becomes. It's a basic rule of statistics. It's why in baseball, a player with a .500 batting average but only 6 at bats cannot be considered for the batting titles. The larger the sample size, the more accurate the information.
The problem with a monopoly.....if the entire economy was controlled by one giant monopoly (basically, the same results as communism), that one single company doesn't ever HAVE to offer new products. Or they could just arbitrarily no longer offer certain types of products that may still be in demand. They don't have to innovate. Like. Cereal, for instance.
If the entire food industry was only controlled by just a single corporation, that corporation could decide they don't want to offer Froot Loops, or Apple Jacks, or Capn' Krunch. They could keep reducing the number of choices down to just cheerios and Rice Krispies.
What's more, they could dictate the terms of product places in the grocery stores. Hell, they would OWN the grocery stores, and offer practically nothing in choices for all the things. You want a mocha-mint-flavored coffee? Too bad! They could also charge $23 for a gallon of milk and not bat an eye as nobody would purchase it at such exhorbitant prices. Hell, they could just do away with dairy products altogether if they so choose.
You think you're going to open your own grocery store and be able to undercut Monsanto who owns everything? Lol! Not gonna happen, because, you see, Monsanto ALSO owns all of the farms, and they don't want to sell any products to you at all. Or if they do, they can control the prices to be so exhorbitant, that you'd have to charge $32 for a gallon of milk inside your store, because you're paying them $28.
Maybe someone else wants to start their own farm to begin at the beginning of the food industry chain? Haha, Monsanto ALSO owns the banks, you see! Huge tracts of the best farmland is owned by Monsanto. Property prices are really high, so you need to get a loan. $10,000 / acre is what the current owner, Monsanto, is willing to sell to you as a small little ten acre corner lot. $100,000 for ten acres of land, you'll need a loan. $100,000 at 32% interest because Monsanto Bank can do that, and you don't even have any cows, seeds, or equipment yet.
The best such a society could possibly hope for, is to have a small "underground" craftsman-style economy for the most basic products. And I mean THE most basic products like....ceramic pots. Good luck to clothiers, considering cotton, polyester, silk, etc would all have to come through.... You guessed it! Monsanto!
They don't NEED information on what sorts of cereal, teas, coffees, style of clothing people want. They won't care. They'll just offer the most extreme basic food choices just to keep their workers alive, working, and producing the next batch of workers as they grow taller.
Now. That's an extreme situation, just to illustrate what monopolistic practices are all about. To prove the point that lasseiz-faire capitalism is NOT the same thing as a free market, and that the larger the share of a nation's citizens that can participate, the better the information and the more that each business would have to pay attention to that information, trends, and styles. They have to innovate, come up with newer and better products. They have to keep their prices at reasonable levels while striking a balance to make a decent profit.
Businesses go under all the time, and that's also healthy for the economy. Business is HARD, as it should be. Like an athlete lifting weights and working out. A species that has to struggle to survive. Humans thrive on a challenge. Hell, it's why we play complex Paradox-style strategy games! They're hard, and it's fun. You're forced to use your brain. Businesses that go under, improves the information. Maybe their business practices were bad in general? Maybe the products they offered nobody wanted? Maybe the location of their business was bad?
The latter point, bad location, is very useful information for civic and city planners. It's one way of how city managers, local politicians, emergency services, and even state and national departments of transportation make key decisions on infrastructure. How much to spend, when, and where. What needs upgraded.
The east end of town has had a crap load of businesses be abandoned and people move away. Why? Has traffic slowed through there? Are people not able to easily travel in an out because the condition of the roads are crap?
If it were all just owned by a single business and they just simply decided to move out, there isn't much information to be gleaned from that. So Monsanto decided they just simply no longer want to service that area. There isn't a whole lot of insight to be gained. It's just simply arbitrary.