I get the sense that a lot of longtermists are libertarian or libertarian-leaning (I could be wrong) and I don't really understand why. Overall the question of where to apply market structures vs. centralized planning seems pretty unclear to me.

• More centralization seems better from an x-risk perspective in that it avoids really perverse profit-seeking incentives that companies might have to do unsafe things. (Though several centralized nation-states likely have similar problems on the global level, and maybe companies will have more cosmopolitan values in some important way.)
• Optimizing for increasing GDP doesn't seem very trajectory changing from a longtermist perspective.  On the other hand, making moral progress seems like it could be trajectory changing, and centralized economies with strong safety nets seem like they could in theory be better at promoting human compassion than societies that are very individualistic.
• Sometimes people say that historical evidence points to centralized economies leading to dystopias. This seems true, but I'm not sure that there's enough evidence to suggest that it's implausible to have some kind of more centralized economy that's better than a market structure.