You're not mentioning that Hamas dismantles its own water systems to make rockets, Gazans dismantled the export-scale greenhouses Israel left behind in 2005, and Hamas builds electrical systems for its attack tunnels but not for its hospitals. So your analogy is better phrased: "If you lock someone in a basement with systems to distribute water, and they destroy those to attack their jailer, and they scrounge parts to make electrical systems to shock their jailer rather than run their own ventilator, and you give the jailed a greenhouse to grow vegetables but the jailed destroys it, well, who's to blame?" Uh, the jailed, obviously. But they're not actually jailed. Up until 100 years ago, almost no one ever traveled further than a few miles from their place of birth ever during their entire lives. For Gazans to be restricted to Gaza is very reasonable, especially consider that they tend to build attack systems rather than systems for their own benefit.