Let’s say some extremist, highly organized group manages to successfully assassinate the 10,000 richest people in the world, and then disappears without a trace.

The problem is that these billionaires profit the most from a system of resource exploitation, but they do not benefit exclusively. We'd still have hundreds of billions of dollars in fossil fuel centric infrastructure that we'd need to replace and reconfigure. And that reconfiguration would require a national organized effort.

Ultimate, you can't just wave a wand and make Rich People Go Away. You need a national project that is both popular and efficient. One that reduces emissions while improving quality of life. You need a Green New Deal.

That's not something you can affect purely from subtraction.

You're correct. It would cause some disruption and a lot of joy, but system would continue. It need to be overthrown entirely and new one built. That is, proletarian revolution is needed.

You'd have to also threaten to assassinate their inheritors from taking the estate, or just take the estate. Either way that's violence. The question then becomes is it okay to use the Master's tools to build your own house, to which my answer is no I can't. I can use the Master's tools to tear down their own houses. I may be a bit too idealistic though.