Israel knows that Abbas can't just idle sit and watch as Palestinians are collectively punished. The artificially split between Palestinian brothers by Israel is one split and the real split between them another. Israel by trying to inflame the artificial one is just going to bring the Fatah and Hamas closer together by mutual Islamic demands, but the Israelis are just to dumb to understand that. The risk of the West Bank resistance to pick up and assist the Jihadists in Gaza to fight the occupiers and thus having Abbas looking even weaker not being able to confront the Al-Aqsa crowd, because if he tried then the suicide bombers would move into Israel proper.
U.S., allies stage 20 strikes against Islamic State in Iraq (Reuters)
from the article: ANALYSIS: Israel's real intention behind sanctions on Gaza Strip