Because the RNC paid them to.

They were being released no matter what. The RNC paid them to wait until after the election. In essence they were held hostage longer because of Reagan.

Thought ya oughta know.

http://en.wikipedia.org/wiki/October_surprise_conspiracy

Reagan was also a senile half-wit who couldn't make a decision to save his life. His handlers (Casey, Atwater, Regan, Bush & the gang) his wife, and an astrologist from Hollywood did all that for him.