Yes it's literally very simple. Israel is committing atrocities and relegating 2 million Palestinians to the world's biggest concentration camp where they restrict water, food, medicine, building materials, and energy. They are also bombed on a regular basis. They are not allowed to leave without permission from Israel. The existence of a militant resistance group is inevitable under these conditions, and as their pleas for peace and western liberal sympathy garner no change, their tactics will become increasingly militant. Hamas' existence is the direct result of Israeli occupation - denouncing hamas is like denouncing boiling water. They are the direct results of conditions placed upon them