What mistakes were made on the Island of Ismarus?
In Book 9 of Homer's Odyssey, the title character begins to tell the Phaeacians about his adventures. After leaving Troy, Odysseus sailed to Ismarus, a city that belonged to a people known as the Cicones. [By the way, I believe Ismarus is a coastal town, not an island.]
Odysseus and his men attacked and defeated the inhabitants of Ismarus, but Odysseus' men spent too much time celebrating their victory, despite Odysseus' desire to leave as soon as possible:
Then as you might imagine I ordered us to slip away quickly, but my foolish followers wouldn’t listen. They drank the wine, and slaughtered many sheep and shambling cattle with twisted horns. (A.S. Kline translation)
Thus, while Odysseus' men are wasting time, the Cicones regroup and attack Odysseus and his men. This time, the Cicones gain the victory and kill 72 of Odysseus men (6 from each of the 12 ships). After suffering this loss, Odysseus and his men sail away.
One mistake Odysseus does not make at Ismarus is, as we soon learn, that he spares the life of Apollo's priest Maron, who gave Odysseus the wine that he uses to get the Cyclops drunk.
The men was greedy for treasure so they started plundering the fallen country for gold, so greed took the control over them and started directing them. They didn't listen to Odysseus commands and continuing looting, so as a result, a neighboring city came and invade them and killed a lot of them
One mistake is that the men start looting the fallen city, and get greedy. This leads to them not listening to Odysseus to get back to their ships. Instead, they feast and celebrate on th beach. As a result, 72 men are killed when a neighboring army comes to drive them out.