The Israelis though did support Christian groups who were also fighting the Muslims. It would seem that after more than 20 years of war every Lebanese, whether Christian or Syrian has become tired of fighting and has just decided to "give peace a chance".
Naturally, friction still exists as it always will, but the Lebanese are too entrepreneurial not to allow themselves to pick up and continue building their lives (unfortunately that appears to entail emigrating) after sufficient years of killing.
Alliances with the Israelis were Maronite initiatives, and the Christians did not form one front (nor did the Maronites themselves). Political affiliations played their role, too (communism for example is a strong pillar of identity for its adherents of whatever religious faction), as did Israel's involvement, the switching of sides (observe the Syrians), and intra-religious and intra-sectarian fighting.
Jordan and Black September factor in as well.
As for the rape pictures, I cannot comment on their veracity, but that Israeli soldiers would commit such acts should not be surprising.
In IC XC