He shouldn't. Sounds like it's not a good deal.
Israel would end the blockade (needed to keep Hamas from smuggling in weapons/materials needed to manufacture weapons) and Hamas, still in charge of 100% of the Gaza Strip after Israel's withdrawal, would pinkie-promise not to rebuild its arsenal. Of course, after lifting the blockade and it having been lifted for a while, the diplomatic blowback to Israel from reimposing it if Hamas reneged on its end would be considerable. Meaning Hamas could probably get away with a slow rebuilding of its capabilities. And with unrestricted access to the high seas, who knows what sort of fancy toys they could import?
What did Hamas and the people of Gaza get out of this? Everything and nothing. On one hand, they were ultimately rewarded for the murder of 1,200 Israelis. Hamas will be able to tell its constituents "See? Extreme and indiscriminate violence against Jews works! It got the blockade (in place since 2007) taken down! Let's do more of that in the future!"
On the other, they'll still be living under the thumb of totalitarian jihadists and Israel's going to have to do this all over again in 5-10 years. They'll have to kill another 50,000 or so Gazans, and sacrifice however many of their own soldiers were killed doing urban warfare again. The 50,000 or so who died this time around died in vain, because their deaths did not secure any sort of lasting peace.