A couple of thoughts:
One: Musharraf pardoned her (or just dropped the charges) for her corruption during her Prime Ministership. He did this to try a power sharing arrangement and gain credibility and a wider base of support. It might not have been in his best interest for her to be martyred. The PPP is going to take full advantage of this, and even if they don't have a replacement as charismatic as Bhutto, they might do much better in the election than if she were a living candidate.
Those elections, by the way, are only ten days from now, if Musharraf does not cancel them.
Two: The canonization of Bhutto. I used to be a big fan of hers - I liked her economic and social policies, and her attitude towards the west (she is a London School of Economics grad, after all). Then her husband and her started to steal the treasury, and she went soft on the Madrassas - incubators for Al Quaida (sp?) and the Taliban. She agreed to come back to Pakistan, knowing this would lend support and credibility to a dictator. She could have come back any time, remember, on her own and owing nothing to anyone - she simply would have had to face the charges. Nevertheless, she will be canonized as some sort of feminist icon. Women - choose your role models with care.
Bhutto was smart, brave, dedicated and committed to democracy. She was also corrupt, opportunistic and not terribly different from most other politicians.