You often see reports after a successful attack that "so-and-so warned such-and-such about this-and-that days before attack", but they almost certainly get dozens of warnings a day from lots of sources. Some are right, some are wrong. The attacker only has to be lucky once. The defender has to be lucky every time.

That's not to say that Israel won't capitalise on the chance to flatten Gaza, because I browsed /r/combatfootage and have eyes, but I think they'd rather not have hundreds of Israelis held captive and over a thousand dead.