We don’t know how pterosaurs evolved powered flight. The most primitive, probable, ancestor of pterosaurs had a bodyplan closer to that of a kangaroo. And the earliest pterosaurs like Preondactylus or Eudimorphodon were already fully capable of flight.
Plus fossils can form, emerge, and erode away before humans even evolved, thus removing our chances of knowing about species that DID have a chance to fossilize, all because bad luck said the geology between now and then would fuck our knowledge over.