Therefore the RN is going to be weaker in the Mediterranean and North Atlantic. So there might have been no German paratroops to take Crete, but the planned amphibious landing got through because there were no British cruisers and destroyers available to sink the convoy, which is what happened IOTL.
But the Kriegsmarine's surface fleet is going to be just as strong in the aftermath of a failed Sealion because all but one of the big ships (i.e. the Hipper) would not have taken part in the disaster because they were either still under construction or under repair.