I think he and his family was threatened by the Obama Thugocracy.
I have seen that theory being bandied about ever since the decision. They claim he had illegally adopted children from Ireland and Obama used that to threaten him.
My own theory is that he was so inspired to demonstrate how non-racist he was (virtue signaling) that he bent himself into legal contortions to rescue the signature legislation of the "FIRST BLACK PRESIDENT!"
I have a lot of reasons for believing Roberts is so in love with the idea of a "Black" President that he would eschew common sense in his Obamacare decision, but i'll just mention one.
Robert's Flubbed the Oath of Office which he administered to Obama. I interpret that as his being so emotionally involved that he couldn't keep his thoughts straight.
He was so aware of the "HISTORIC" significance of the event in which he was participating that he became emotionally choked up.
Roberts is a "Black President" groupie.