The followings are guesses, but every guess has a factual root
1. Hamas is upset with Fatah’s attempt to reconcile. See this link
2. Egyptian Muslim Brotherhood wants a war in Gaza to bolster their position as wanting to end peace agreement and enter war with Israel, meaning - this is what qualifies as an "election campaign" in the new Arab world.
3. Hamas headquarters in Syria receiving commands to divert attention from massacres committed within Syria against uprising
4. Iranian global strategy to ignite the middle east
5. Soros lead global lefty scheme to ignite war which will force Obama and NATO to activate forces against Israel to protect Gaza civilians much as it has in Libya
6. Qatari Muslim Brotherhood headquarters orchestrating Arab world havoc and advocates it through Al-Jazeera
Follow links for more details. Whatever the reason is – Israel is its final target.