As any 6 year-old with simple math skills would have predicted, the basic economics behind Obamacare were not sound and thus the main policy initiative of America’s Modern Messiah was doomed to failure. Richard Epstein, of the Hoover Institution, gives the details in this podcast.
Many more facts about this ill conceived program can be found here:

And what the insurers who have left the program have made clear is that they believe that, absent changes, the losses will go on forever. “The vast majority of payers have experienced continued financial stress within their individual public exchange business,” Aetna CEO Mark Bertolini said about the decision. In a call with investors last year, a representative from UnitedHealth said the company “saw no indication of anything actually improving” inside the exchanges. “We cannot sustain these losses,” UnitedHealth CEO Stephen Hemsley said on that call. “We can’t really subsidize a marketplace that doesn’t appear at the moment to be sustaining itself.”

As with all Leftist failures, expect no apologies or mea culpas. They’re incapable of it. With an endless stream of supporters whose memories are shorter than that of a gnat, they will just move on, setting their eyes on the next part of the economy to destroy.