David, I think you hit on some good reasons why so many states failed here: The Feds left the door open to the states to do as they saw fit, but the states were ill prepared to take on the kind of projects these exchanges ultimately became. That Massachusetts, the state that should have had the most experience, and usually has a good IT record, failed to deliver here also suggests the complexity of these sites -- as you say, they are far more than just web sites. One would have thought experienced hands could have seen that coming.
The bigger failure in a way is that so much duplicative effort went into buiding these sites. I think you're right, the fact that politicians got to spread a lot of money must have seemed attractive at first. But it looks like they mostly threw the money down the drain.