I wonder if GW Bush and his proxy Alberto Gonzales, who supposedly vetted Roberts, didn't nominate Roberts because he would likely make a ruling as he ended up doing on AZ's SB1070.
It could be the "Affordable Care" ruling was just collateral damage.
Lethal to the Republic, but collateral.
I think they nominated Roberts because the Senate, bullied by Chuck Schumer, was making idealogy an issue in Judicial confirmations. Schumer was running around yelling "extreme" to any of Bush's nominees, including Janice Roders Brown, Miguel Estrada, and Charles Pickering.
Roberts appeared smooth, not extreme, and his hearings where he did not refer to any notes impressed many people.
He was selected to cancel the "extreme" charge from Schumer.