How Britain and America expanded trained wartime crews

Why did British and American wartime-trained crews do better than their peacetime-trained crews, unlike the German experience?

They did not necessarily perform better. Britain and America began with larger trained bases, built mixed-experience crews, and used experienced personnel to train others.

The question's premise needs qualification because wartime-trained crews did not necessarily outperform peacetime professionals. Britain could draw on regular personnel, the Royal Naval Reserve and the Royal Naval Volunteer Reserve to provide trainers and experienced cores for expanding crews. British and American naval aviators also returned from operational service to instruction or other shore appointments, passing combat experience to new personnel. Eric Brown's move from escort-carrier service into test flying illustrates another use of operational expertise. The comparison with Japanese practice concerns how personnel were managed: keeping successful aviators continuously in combat denied later recruits some of that experience.