Two reasons if I recall.  One = cost.  Moving to a Div I program would have cost considerably more for scholarships and facilities than what we could afford in the late 70's.  The NCAA required all institutions to compete in all sports at the same level (Example: D-I, D-II, D-III) with a few exceptions (hockey and soccer). So we had to move to D-I if we wanted to maintain a swim program. Also, the Sun Belt Conference had few, if any swim programs.  This made it difficult to schedule, recruit and promote the program.  Most of the teams in D-I with programs nearby were super powers (UF, UGA, etc,) which would not have helped us much as we would have had to try to compete with them on the cheap.  The decision  was to align our sports offerings with the other institutions in the Sun Belt (CC, volleyball, softball, golf, soccer, etc.). Normal