How does the existence of a paperclip maximizer rest on the assumption of recursive self-improvement? Making nanotech weapons to stop humans from shutting you down and thereby reducing the expected number of paperclips doesn't require exponentially increasing amounts of intelligence. It only requires a fixed amount of intelligence.

Also you should justify "this is clearly [1] not the case". You're probably taking the "necessarily" phrasing really literally, instead of as "with non-negligible risk", and thinking of corporations or evolution as "superhuman"? On the other hand, evolution and corporations respectively did and plan to produce smarter entities so that's not so clear cut.

1: https://medium.com/science-and-technology/how-to-spot-a-weak...