Just in brief, ignoring some history and so on, Gaza has been under Israeli occupation for a while now, controlling essentially everything that goes in and out, including people. Hamas gained power there, and legit, the Israeli government has given resources to Hamas to keep them going, supposedly as an excuse to keep their thumb on the Palestinian population.
A lot of people supported the creation of a Jewish state coming out of WWII and the holocaust, but currently, and especially because of just how hard the Israeli military is going now, it's becoming impossible to not see how much the Israeli government just wants to take control of all the land and wipe out the Palestinian people.
Of course, there's more going on, and some people might disagree with my simplification, but I think this is as good of a simple explanation of at least my understanding trying to follow what's been going on in the region since the early aughts.