Bush is a Republican and therefore spineless. He signed the bill because that was the easy thing to do, just as he snorted fire for most of last fall because everyone else was snorting fire.
Those who believe that all his recent wobbliness is part of some fiendish plot to surprise Saddam are probably still waiting for the Special Prosecutor to leap out at Clinton and shout "boo!" Sorry, folks, Ken Starr is Mr. Republican and Bush is following in his footsteps.