Loose sloper antena puzzle.

Hello all. Lately I have been using an end fed 40 ft wire with a 9:1 unun for 11 metre dx. It was intended to be a sloper but I was struggling with high swr. I tried it in many positions and my last attempt I tried the radio before drawing the wire tight so the wire formed a curve from 25 ft down to 6 feet of the ground. To my suprise the swr was very low and I tried a contact in  Sicilly and he reported I had a strong signal and very clear with good modulation. I have now used this antena for many long distance contacts to over 3000 miles but I have never heard any stations closer than Finland or southern France so probably 800 miles. Can someone explain this. I understand the theory of propagation but the high swr with the tight wire and very low swr with a loose curved slper  along with great dx range but nothing for 800 miles is puzzling.