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First time posting a question here. Here goes.
So I know that most submarines of WW2 were more along the lines of a submersible, where they would spend most of the time on the surface, then only submerge for attack or to evade detection. To my knowledge, the US fleet boats and the U-boats all did this, with the exception of the Elektroboats, which was designed to operate largely submerged. After the US studied the Type XXI boats, they developed the GUPPY upgrades for their own Gato, Balao, and Tench fleet boats. Soviet post-war subs were basically Type XXI copies.
How much of a "shock" to submarine design/doctrine was the Type XXI? It seems like right afterwards most nations immediately abandoned the old "submersible" design to pursue the Type XXI design. Did it really render the old "Fleet Boat" obsolete that quickly?
Also, were there any equivalent allied projects? While I understand that the U-boat war in the Atlantic was a vastly different battlefield than the submarine warfare waged against Japan, I'd think that the allies would have also liked a submarine with capabilities similar to the Type XXI. After all, they did largely move to that sort of design after the war. Was the US not interested because of the vastness of the Pacific? The lack of proper Anti-Submarine operations by Japan? Production concerns?
tl;dr What killed the "Fleet Submarine"? Was the Type XXI really so revolutionary that everyone abandoned the Fleet Submarine idea?
