Getting more equipped troops to Crete in time may have provided the Allies with a reserve force to throw at the Germans. Unfortunately, the rate of the German advance was very quick in mainland Greece, so that troops and equipment were left back.
One easy POD to change that, would have been to have the German attempt to capture the Corinth Canal bridge intact end up as a failure. The bridge is blown up by the retreating Allies, allowing sone more troops to he evacuated to Crete from S. Peloponisian ports, before the Wehrmacht gets there a couple of days later than in OTL. These extra troops are sent with their equipment to Crete and are used against the Germans in Maleme.