NASA had just moved it back either friday or saturday, and back then the chances of Nicole becoming a hurricane were very low. NASA has other time limits too, the batteries, abort explosives, and the solid rocket boosters all have limited life spans.

NASA moved it back to the pad as early as possible so they could meet the next launch time. After that one the next launch window isn't till December I believe. If the launch slips to 2023 NASA will have to bring back the rocket to redo all the things that have fully expired.