To be honest, I don't think individuals leaving Palantir would matter (although it is likely within their capabilities).
Palantir had ~4,500 employee in 2025 as per Wikipedia. Replacements will be found.
To paraphrase my other comment in this post, people leaving a company/vertical hasn't really ever made an impact (I am sure there are edge cases, but I am talking in terms of systemic impact).
It's usually the other way round, things start to happen on the street and then people bail because they don't want the risk/personal reputational damage.