At the start of the war it wasn't clear that carrier-based air power would be able to effectively suppress ground-based air power. The prevailing theory was that carriers were too fragile to do this. The US Army and elements of the Navy with surface warship backgrounds believed this, too.
That turned out to be super wrong, and the Americans won much faster than expected by cutting off and bypassing Japanese strongholds (Rabaul, Formosa) and keeping their airfields impotent with regular carrier raids.
If those hadn't been the case, the Japanese strategy of seizing "unsinkable aircraft carriers" would appear to make more sense in retrospect. The thinking was that an initial crippling blow to the fleet plus the cost of clawing these back would be too much for the US.
Wrong, and in fact many of the Japanese brass thought it was wrong. But irrational would imply that there wasn't a theory, and there was a theory.