The state-run exchanges solution was itself a compromise for Republicans and on the fence Democrats, particularly Arlen Specter, who feared a federal healthcare system would inevitably lead towards universal healthcare. They received their compromise, then refused to implement the exchanges in the hopes that the law would die.
As I understand it it's common for one Dem senator to "take the PR hit" when there are actually multiple members who would not want a bill to pass. A bit of kayfabe.
It didn't, and they're still mad about it.