it's well-accepted that monopolized markets are undesireable in capitalism, so i don't think it's wrong to state it as anti-capitalist. but let's leave the semantics aside.

strictly speaking, unregulated markets don't have to devolve into monopoly, but functional markets are not particularly stable on their own, so monopoly does tend to be a common result. it's like a dipolar chaotic system where the second pole is stronger than the first--once the system flips to the second pole, it's hard to get it back.

even regulated markets can devolve into monopoly, as we all well know just by looking around. the early 20th century compromise was to allow monopolies to form but strongly regulate them. over time, we've allowed moneyed interests to weaken those regulations, with the entirely predictable result of the current imbalance of wealth distribution and social unrest.

Points taken. Well-said.