Republicans refused to appropriate money needed to implement Obamacare. When Sebelius tried to shift money from other areas to help do what needed to be done, she was attacked by Senate Republicans. At every step, Republicans fought measures to get money to put towards implementation.
Is it really a surprise then that implementation hasn’t gone smoothly?
Federal legislators aren’t the only ones to blame. Let’s remember that original versions of the bill called for one big national exchange. This would have been much easier to implement. But conservatives declared that insurance should be left to the states and kept out of the hands of the federal government. So as a compromise (yes, those did occur), exchanges were made state-based instead of national.
As a precaution, the law stipulated that if states failed to do their duty and enact exchanges, the federal government would step in and pick up the slack. This was to prevent obstructionism from killing the law. Surprisingly, it was many of the same conservative states that demanded local control that refused to implement state-based exchanges, leaving the federal government to do it for them.
That made implementation much harder.