The Senate bill had $2 billion. The legislation coming out of conference "compromised" on $8 billion.
How did this happen? Well, some of that $8 billion, as the Washington Post reported Friday, seems intended for "a controversial proposal for a magnetic-levitation rail line between Disneyland, in California, and Las Vegas, a project favored by Senate Majority Leader Harry M. Reid (D-Nev.). The 311-mph train could make the trip from Sin City to Tomorrowland in less than two hours, according to backers." Reid of course played a major role in putting together the final bill.
That's the kind of policymaking the new Obama administration has embraced in its signature legislative proposal: a congressional process as unseemly as ever; an emergency bill that barely addresses the emergency; a "stimulus" bill short on stimulus (is that magnetic-levitation rail line "shovel-ready"?).
What accounts for this debacle? You could start with a lack of presidential leadership.