Hamas can and do control, infiltrate and intimidate anyone or any organisation in Gaza that they want - but even so, there are many people and organisations who do essential work there despite the ever-present threat of Hamas's influence/harassment.
Unfortunately, Israel are treating nigh on everyone in Gaza as if they are complicit in Hamas's actions, which amounts to collective punishment - something Israel has meted out to Palestinians for years, against international law. What Israel is currently doing in Gaza beggars belief and is unconscionable - but yet, Hamas bear as much responsibility for visiting this tragedy on the people of Gaza, and indeed one suspects that the higher-ups in Hamas, the wider region, Qatar, Iran and Russia are very likely delighted with what is currently happening in Gaza, because Israel is taking the bait - they want Israel to take enough rope to hang themselves with, and their western backers to boot.
Meanwhile, civilised people the world over can only watch in abject horror as Gaza descends into hell, with one side committed to illegal and grossly immoral acts of collective punishment/genocide, and the other side more than happy for them to do it.