I had this discussion with my brother in law while drinking one night. He was going on about the free market or something and we sort of just talked through how the market could be free like people say. Organically we both realized just by talking it through that there's no way the could be a "free market" because the rules are always backed by state violence or the threat thereof.
But beyond that, as certain companies succeed, they grow. As they grow they kill competition either by absorbing them, by out competing them, or by using vast resources to kill them through attrition. As they continue to grow they diversity to try to gain further advantages. They begin to control their supply chains and own the resources that ensure even their would be competitors become reliant on them, essentially neutering potential competition. They corner markets. If there were a "free market" it would end up as a single company that owned everything. At a certain point a single company would become so integral and so powerful that it would control the government, the banks, and all the resources and it would care nothing for anyone outside of the people who keep it in power and control.

Obviously this isn't how things are though. There isn't a "free market", instead there are cabals that rig the system to keep themselves on top but none seem to gain enough advantage to kill off each other to take over entirely. There are likely many reasons why that hasn't or maybe can't happen outside of a singular perfectly seized opportunity, but the resulting situation we find ourselves in is hardly any better. It's close enough that most people in the world are deemed unimportant and expendable, if not detrimental.

I don't think that we disagree. Because, for the reasons that you have provided, competition will produce almost-indestructible monopolies as a natural consequence, and those monopolies have a tendency to use their extensive power to destroy and buy out potential competitors and seek for quick, easy ways to accumulate wealth; notably, through rentier capitalism.

This is literally what's happening right now; at least, in the US.

People are led to believe that industrial competition is like a sports league where winners just get a trophy and the competition resets every year 😂

Until they become too big and buy every potential competition out while they are still small.