It was the peacenik Leftist Israelis who vaguely supported Hamas, just as they supported Arafat. The great blowback would be the outcome of Oslo, where Israel provided the PA with guns, and training only to have it turned back on them. Hamas was not built up by Israel, unless you consider the 70+ trucks of aid meant to go to Palestinians as somehow supporting Hamas.
http://www.ynetnews.com/Ext/Comp/Art...651783,00.html
None of these so called Palestinian groups should have ever been legitimized in the first place.
The divisive climate within the Palestinian factions traces outside the conflict. It's not an Israeli fabrication or manipulation, even though Israel has thought they could use it to their advantage at times. Pan-Arabism has never worked for obvious reasons.