Then explain why the largest capitalist government can't do that.

It could, it just doesn’t want to. Or at least the inertia and obstacles of gaining enough political support for doing it, paired with the reluctance of the powerful entities that gain from the existing system, prevents it from happening. But there is nothing that makes it fundamentally incompatible with still allowing private enterprise and profit

Fundamentally, not paying for externalities is why it "succeeds". It's foundational. As I stated at the top.

Capitalism succeeds even where they do pay for externalities, so you are wrong.

really, is that why all these brownfields were abandoned? We got billion dollar contamination everywhere that no one wants and random people suffer.

It's simply a failed accounting system you have.