In no way am I defending Palantir, but literally any random official or intern could've created this with any random AI generation model. It's not like the government is requiring people use any kind of ACLs or officially approved software to do stuff anymore.
Palantir has an image generation model? It seems to me that Grok is the most likely as its already on the network where the image was posted and is known to be used for this sort of thing. Gemini has no problem creating the image from the source either.