Early in the war, incomplete bases and an unsecured Channel forced the Grand Fleet to operate along Britain's west coast. Scapa could become the main fleet position only after the Channel was protected by barriers, minefields, pre-dreadnoughts, and supporting forces. From the Orkneys the fleet could steam south against a German sortie instead of approaching from the side, improving the chance of cutting the High Seas Fleet off from home. That geometry explains why Britain accepted severe basing inconvenience once the southern exit had been secured.
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Why the Grand Fleet needed Scapa Flow in 1914
Once Channel defenses were in place, Scapa Flow let the Grand Fleet come down on a German sortie instead of approaching from an awkward angle.