Why the Regia Marina did not challenge the Malta air plan

Did the Regia Marina object when the Regia Aeronautica claimed it could neutralize Malta?

No. The navy was content to let the air force believe it could do the job because that kept the rival service occupied.

The Regia Aeronautica was confident it could knock Malta out of the war. The Regia Marina raised no objection and was content to let the air force pursue the task. That confidence kept a rival service occupied and out of naval planning, even if the assessment proved optimistic.