Strategically, I think Malta was the key.
Without Malta, even a stronger commitment by Hitler to support the Afrika Korps would have been a waste of materiel for without a guaranteed supply of fuel, the armoured forces were impotent.
Moreover, given a greater commitment by Hitler to the desert war, any advance by the British would be hampered by not having secure fuel supplies.

Malta was the final bastion of power in the Med. Without her, British endeavours in the desert would be seriously compromised.

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