The AI was fully convincing.
Musk is getting some small amount of stick for having re-posted without a clear disclaimer that it was entirely AI generated and a parody. The content (IMO) made it clear that it was a parody, so I didn't really mind that it was re-posted without the disclaimer. (And I would vote farther Left than Musk, probably for Harris.)
I think the story about this video is more about the fact that the AI is so danged visually effective and accurate, and less about anybody trying to actually pass these clips off as truthful reportage. Yes it looks very real. No you didn't try to make us think it was real.
But there were other true-fake a.k.a. deep-fake videos distributed here and there which claimed to be the "real" Biden or Trump. I didn't keep careful check on them, but I know it's going to be more and more of an option for any side. Disinformation was spread about the knife assailant at that small-kids' dance party setting in England, and then deliberately re-posted by extreme-right hate-mongers who wanted to mislead the public and whip up false fervor over the immigrant question. It didn't really use much AI, though a small amount was used to create the text of the initial story out of (IIRC) Hungary and India.