I agree with your analysis but Greek weren't merely conqueror, they are part of Sicily because they established themselves there and remained. Large part of Catania and Syracuse are of Greek ascent.

About the arable land, I don't know, Sicily is extremely fertile in general and there also some large plains as well like in Palermo. Sicily was extremely rich and prosper during the Normad period and for the Arabs who came before it was nothing short than a paradise.