Michael Oren and Yossi Klein Halevi say it's all about Iran:
If Israel successfully overthrows Hamas in Gaza, it would strengthen anti-Iranian forces throughout the Mideast and signal the region that Iranian momentum can be reversed. The Israeli military operation could begin the process that topples a terrorist regime that seized power in the Gaza Strip in 2007 and has fired thousands of rockets and mortar shells into Israeli neighborhoods.
And whether or not Hamas is ultimately overthrown, Israel can achieve substantial goals.
The first is an absolute cease-fire. Previous cease-fires allowed Hamas to launch two or three rockets a week into Israel and to smuggle weapons into Gaza through tunnels. To obtain a cease-fire now, the international community should recognize Israel's right to respond to any aggression over its international border and monitor the closure of Hamas' weapons-smuggling tunnels.
Above all, the goal is to ensure that Hamas is unable to proclaim victory and thereby enhance Iranian prestige in the Arab world.
The trouble with apocalyptic movements like Hamas is that they will proclaim victory regardless, no? Hamas will only be defeated by the Palestinians, in the end. Which is why Kramer's notion of pitting the PA against Hamas makes more sense. But the idea that this time, pure violence and enforcement of a blockade will force a change of heart among Palestinians and Arabs more generally seems utopian to me. The risk is that this could ignite pro-Iranian Jihadism across the region.