Perhaps, too, they felt that most Shi'ites were simply willing to buy into temporary American occupation and decided to follow the path of least resistance. One thing I noticed from the coverage of the meeting was that the exile opposition leaders were the ones calling for a quick withdrawal, while the leaders of groups within Iraq wanted the U.S. and U.K. to remain and help rebuild. Even the great pilgrimage to Karbala seems not to have been as huge an anti-American outpouring as some media reported. Al-Jazeera, for example, focused mainly on a day of religious rejoicing and relief that Saddam was gone, while "some" also warned the U.S. against a long occupation. This was also what I saw from various wire services.
The other two main Shi'ite factions were unrepresented at the conference, which makes SCIRI's move even more interesting considering that the main clerical establishment in Najaf is the one considered most pro-American. Also, the demonstrators outside the meeting all kept calling for "one Iraq." If that's the major demand of the day, we're in good shape, as I have yet to hear anyone on the planet call for anything else.