Complex sentence: Bills were lost because the two houses could not agree on a single version, and conference committees that were created to reconcile different versions of bills often met in secret, and were thus unaccountable for their actions.
Split into simpler sentences: Bills were lost because the two houses could not agree on a single version. Conference committees that formed to merge the two bills coming out of each chamber often met in secret, and thus were unaccountable for their actions.