As soon as you have an entirely new power structure you have a new government.

Different people may be on top, with different aims (...arguable, but let's pretend.)

But there will always be a government of some sort making the big decisions for the benefit of its ruling clique.

>But there will always be a government of some sort making the big decisions for the benefit of its ruling clique

That depends on how much resources said government can extract from the environment. Either by taking or by providing value in exchange.

One can imagine a level of technological advancement that makes violence impossible and trade unnecessary. Poof, no government.

Indeed. That's the point. We can't sidestep human control via technical means.