Centralization is a logical result of unregulated capitalism. If money can be used to buy advantages in the market, it follows that any player with an edge can use it to widen their lead over time to the point nobody else can compete.
Anti-trust regulation is supposed to solve this, but in the US at least it seems we've settled on a status quo where we pretend having two giant players in a market rather than one is enough to protect the interests of consumers, despite many many examples where that has proven not to be the case.
Only if it's provably harmful. And only if you hire people into the anti-trust regulation role who are perfect uncorruptable beings that can see the future consumer implications of each business decision.
Given the regulators we've hired so far are neither, we shouldn't be assuming regulations can solve this.
In reality, regulations give a big first mover advantage. It's much easier to incorporate regulations when you're up and running than come in as a new competitor and slam into a wall of red tape, which due to years of relationship built up is much more porous for the incumbants.
Anti-trust regulation is supposed to solve this, but in the US at least it seems we've settled on a status quo where we pretend having two giant players in a market rather than one is enough to protect the interests of consumers, despite many many examples where that has proven not to be the case.