Why navies pursue old and new technologies together

Why continue the battleship caliber race instead of shifting entirely to carriers?

Because navies needed the best proven technology as insurance while the new carrier system remained uncertain.

The largest battleship guns and the aircraft carrier were not mutually exclusive research paths. Navies could recognize the promise of aircraft while remaining uncertain about whether carriers could reliably perform every capital-ship task. Continuing to improve legacy weapons preserved a proven combat system if the new technology failed or matured slowly. The resulting overlap was therefore an insurance strategy rather than simple refusal to recognize naval aviation.