Its fairly obvious from day 1 that the IDF knew that Hamas were planning an attack but Israel has been worried about the growing power of Hamas for years and they wanted to give Hamas "enough rope to hang themselves". That meant the music festival attendees were used as bait, they were sacrificed in order to show the world what mongrels Hamas were and to give the IDF a good excuse to wipe them out that they would not have otherwise been permitted to do.
Trouble is the IDF underestimated how entrenched into Palestinian society that Hamas was, the IDF simply can't take out Hamas without creating absolute carnage in Palestine so they have made the decision to sacrifice as many Palestinian men, women and children as needed to permanently take out Hamas. That killing of innocents has turned world opinion against the IDF but they don't seem to care. I suspect the IDF sees every Palestinian child as a potential future Hamas operative so they don't seem to worry about cutting their lives short but the world correctly views that as barbaric and it won't be long before rightly or wrongly Israel will be seen in a similar light to Putins Russia, a blight on world society.
