Shackleton is a great leader for many reasons; if its an 'all of the sudden' crisis, he always knows what to do, he always remains calm in any situation and reacts appropriately, and Shackleton runs a tight ship but he is always fair with his decisions. When the crew signed up for the Endurance they knew what they were into so having a great, supportive leader is important when setting sail for many months even years.
When the Endurance got stuck in the glaciers what did Shackleton do? He didn't panic nor did he stop giving men their daily chores. He told all of the men that they will wait it out and that orders are still mandatory. Eventually the Endurance couldn't take it anymore, it sank. All the men were a little panicked with little food