Hamas was fairly elected. Israel and the US were the ones that interfered because they didn’t like Hamas trying to go legitimate.
And no, just no. This is not Just War Theory. In Just War Theory you don’t carpet bomb residential areas. You don’t make the Hospitals main targets and you certainly don’t repeatedly attack and kill plainly marked journalists standing in the open. You cannot commit war crimes and then claim it falls under Just War Theory. That’s the complete opposite of that theory.
And it’s a collapsed state because Israel ensured that, by preventing the legitimate winners of the election from taking power peacefully, by blockading them when the people who voted for them rightfully put them in power anyways, and by repeatedly attacking them over the last couple decades, claiming any government official was a terrorist including civil servants running the basic infrastructure of the region. You cannot punch your neighbor in the face, and then move into his home on the theory that he’s in the hospital now and call it a moral argument.