The republicans had the governership for years during that time, and also controlled the state senate for part of that time.
Who held the Governorship is only relevant to a potential vacancy, otherwise if you add up the total number of members in the Assembly and Senate since 1975 onwards, it is overwhelmingly Democrat (the Senate fell in 2009 to the Dems after being in continuous GOP control since 1966, but that wouldn’t have mattered because of the huge Dem majorities in the Assembly since after 1975).