Judging from the amount of supplies they brought with them, they were not planning a raid, but a conquest. They intended to stay and hold the ground they had captured.
During the day IDF units from all over Israel were rushed to the area, with speed taking precedence over organization. These units rushed to counterattack the Hamas troops. Gradually more units arrived in a more organized fashion and began fighting to take back the villages and extricate the survivors.
The new information shows a very well-thought out plan, executed by surprise and exploiting that surprise by rushing into Israel at high speed (motorcycles and all-terrain pickup trucks) against a numerically greatly inferior defense force dispersed over a very wide front.
However, given that Hamas intended to hold on to the ground it had won in the first rush, not only massacre the population, this second portion of their plan failed. I can only assume that since the Hamas leadership are well aware of the overall ratio of forces they did not expect their force to hold the ground indefinitely, but apparently they did intend to hold it longer than they succeeded in doing...