They may destroy their creations but that would be a minor blip in overall system that will keep moving. Destruction of Facebook, Amazon, SpaceX won't destroy social media, eCommerce or reusable rockets. Previously destruction of giants like IBM/Apple(1st round)/Cray/Sun had no impact on PC, GUI, Supercomputers, Servers or any other fields they were pioneer in. Even if OpenAI/Gemini/Anthropic all disappear immediately the void will be replaced by something else.

That's actually a quite good high-level measure. However, I'd question your measurement: I doubt that Musk, Zuckerberg and Thiel would actually be able to destroy their creations. SpaceX, Tesla, X, Meta, Palantir - they're all large organizations with many stakeholders, and their founders/chairman do not have absolute control over them. The result of any of those individuals attempting to destroy their creations is not guaranteed - on the contrary, I'd expect other stakeholders to quickly intervene to block or pivot any such moves; the organization would survive, and such move would only make the market lose confidence in the one making it.

There's no total ownership in structures as large as this - neither in companies nor in countries. There are other stakeholders, and then the organization has a mind of its own, and they all react to actions of whoever is nominally "running it".

You can also measure agency as the power to destroy other things.