There were numerous reasons and they were mostly related to fragmentation of the movement. For starters, there were multiple factions and they didn't work together because they believed that the fight should be led in different manners. One faction believed that it needed to be peaceful while the other that they should become militarized. Later as they started getting some rights people started becoming satisfied with it so they didn't want to fight more. As leaders started getting assassinated many people started getting disillusioned with the movement because they lost the will to fight.
