Which, quite frankly, was stupid. It was pretty clear from the outset the ACA would break the US health care system so badly single-payer is the only option going forward.
They also had enough political experience to know getting the (delayed) more unpopular parts (like cuts in payments to doctors accepting Medicare, increases to penalties for people who don't buy insurance, and extra taxes for "Cadillac plans") might be too difficult to get through when the time came. That's why they were delayed.
I suppose I can give them enough benefit of the doubt to say many of them may have believed once the system was in place they could solve the problems by closing the gap with something something.