I suspect Israel has invaded Gaza for the same immediate reason it went to Lebanon a couple summers ago. Rockets, or more accurately, to remove Hamas' capacity to strike at Israel by launching a disproportionately violent response to strikes by homemade rockets. Nevermind casualty proportionality or any of that feel-good liberal nonsense about applying humanity to war or taking the high road to peace. The Israeli leadership, as much as the Palestinian leadership has simply gone mad.
Why? 60 years of the bastard conflict born to prevent a repeat of the Holocaust and bungled by the surgeons of transplanting dying imperial organs with a new state, but with anti-rejection medication toxic to the other organs has probably so polluted the system that there really is no hope for peace.
The ironies are compound and terrible. A state formed in part as a response to the genocide of one people now finds itself all but committing the genocide of another to survive. The birthplace of the person Jews, Christians and Muslims all consider a prophet of a their God and a prince of peace becomes a catalyst for bloodlust. If you think about this too much, you'll want to pull your hair out with the pointlessness of it all.
Play it out. Imagine an Israel or a Palestine that exists because it managed to survive by committing genocide against its neighbours. To what proud history could that new nation possibly lay claim?
Play it out again in real terms. What happens to the US lifeline providing Israel with the firepower to maintain the status quo when the US hits the second Great Depression. What happens to Israel when hyperinflation destroys the US dollar? The odds change, that's what happens. If the same people are in power in the Territories, Israel and some other places, then nothing will survive. If the peacemakers find themselves in power, there is a chance, provided the warmongers do not spoil it by ripping their respective polities apart.