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.

Not to mention, organizations don't just blip out of existence. A dying giant leaves behind assets, IP, and people with know-how and experience - all ready to be picked up and stitched back together, to continue doing the same thing under new ownership.