Greece would probably still fall for the same reasons as in the historical campaign. Crete's fate is judged differently because an Italian fleet under greater pressure would have less freedom to help capture the island. Retaining Crete could put oil fields critical to Germany and Italy within range of heavy bombers. That further effect depends on both keeping the island and being able to operate those bombers there.
Notable Point · 40:09-40:43
Holding Crete and bringing Axis oil fields within range
Retaining Crete could give heavy bombers access to Axis oil fields, provided the Allies could operate them from the island.