They would have adopted the M1 Garand sooner IF they had been given the chance to have it and it wasn't the higher ups in the Navy. It was the Army refusing to release it to them. That is why they had to use the Johnson rifle and were very surprised by it being as good as it was. If it had been a better bayonet platform they very well may have kept the Johnson but the thin barrel didn't support use of a bayonet very well.