All they have to do is stop firing rockets at Israel. But in Arab world, if you stop killing Jews, you lose popular support, then the next generation of "freedom fighters" comes along and kills you. That's how Hamas came to power in Gaza. That's what will happen to Hamas itself if they ever stop killing Jews. So, even if there are people in Hamas who would like to stop firing rockets, and develop gas field instead, they simply can not.
Donald Trump: Israeli settlement construction in West Bank should 'keep going' (Haaretz)