Just plopping one of my occasional reminders that this war is 3,000 years old (or older, depending on your interpretation of recovered tablets).
The Gaza Strip is where Philistia was. If you aren't familiar with the Biblical bad-mouthing of its people, you'll still be aware that 'Philistine' today means an ignorant yob with no appreciation for culture. The Philistines weren't yobs - Philistia was such a prosperous region, producing precious things like purple dye and coloured glass, that other powers were constantly fighting for control of it. These included the Israelites.
I always thought the god of the Torah forbade the Israelites to overwhelm Philistia, but I must have missed some nuances because they've been at it for millennia!
Also see Palestine = Canaan -> Israel. Philistia was eventually squashed out of existence, but its people migrated further south into coastal Canaan and later to North Africa.
The entire history of the Israelites, as drummed into most of us at school, is about destroying neighbouring civilisations to take their land and wealth. It's fair to protest that it was the main business of all governments back then, though not all were quite as brutal. Cities and peoples were represented by their gods, so killing a population was the exact equivalent of killing their gods.
Though the world's changed radically since the early iron age, it doesn't look like people's thinking has kept up. The gods are fewer and bigger now, providing excuses for even bigger wars.
[TLDR: It's about land; excused by religion; escalation of ancient ongoing rivalry.]