Israel never could have launched this extensive a military campaign with international support on the basis of an intelligence report from Egypt, Mossad or otherwise. People would say that any time someone wanted to invade a country without provocation, they could just accuse the other side of wanting to attack. It's also possible that Netanyahu knew of a planned attack but not of the severity. Netanyahu is a hawkish zealot, obsessed with reclaiming the West Bank. It's not hard to imagine an aging political leader wanting to take over the settlement as part of his legacy.
I don't think that there is some kind of conspiracy theory here, but there is no reason you'd need an invasion to stop the attack. Simply refraining from moving soldiers outside the Gaza border and into the West Bank would have been sufficient. It was 3000 thousand terrorists with light weapons, it wouldn't have been difficult to stop if Netanyahu hadn't sent so much of the IDF to terrorize civilians in the West Bank and steal their land.
