Germany gains little from invading a reinforced Greece

Would Greece and Crete still fall quickly if Germany attacked?

Probably not; Greece would no longer be exhausted by Italy, Allied North African forces could reinforce it, and Germany would lack Italian naval support.

Germany could still invade Greece, but the conditions that made the historical campaign manageable have changed. Greece is not already fighting Italy, North Africa is quiet, and the Regia Marina is unavailable. Allied troops from North Africa could reinforce Greece, and Crete is not expected to fall in this version of events. The end of constant Malta resupply would also preserve ships and other assets for the campaign. Germany might threaten neutrality instead because an invasion adds a demanding campaign without solving an urgent strategic problem.