They literally raided for less than a day and than ran back with hostages
That’s incorrect - the Israelis continued to capture and kill them inside Israel even a week after the attack. Some of the terrorists came with provisions that were meant to last for a long time, until the area calmed down, and then to launch a second attack from the inside.
Hamas released videos from the tunnels showing stockpiles of weaponry and supplies. The hostages also testified that they showered every other day, while the rest of Gaza is essentially cut from water supply. Those water had to come from somewhere.