The legislative session began with Democratic lawmakers, advocates and state Comptroller Kevin Lembo all confident that a series of long-sought big ticket health care reforms — including a public option for small businesses — were finally within reach. When the session ended at midnight Wednesday, however, virtually their entire agenda had failed to pass, with several major initiatives dying in the final hours. It was a bitter pill for health care proponents, particularly the death of the public option. In the end, the state’s powerful insurance and hospital interests proved too big an obstacle to overcome, advocates said. As of May 10, the most recent date for which records are available, the biggest and most powerful among them had spent nearly $3 million on lobbying during the session, including $480,079 by the Connecticut Hospital Association and $191,021 by Yale New Haven Hospital.