There have been many revolutionary movements in the Third World over the years, and there have been many specific conditions and developments that have led people to participate in them. If we are to try to say what sorts of conditions and developments have been common to most of these revolutionary movements, we can generally cite a feeling of deprivation and of abuse by the powers that be.
People have generally joined revolutionary movements because they feel that they are not being treated fairly by those who are in power. We can see this, for example, in the revolutionary movement in Mexico in the early 1900s. There, people rose up against the dictatorship of Porfirio Diaz because they did not believe that it was doing much to help the common people. As another example, the African National Congress was a revolutionary movement that was sparked because blacks in South Africa felt that the apartheid regime abused them and took away their rights.
Because there have been so many revolutionary movements in the Third World, the specific events that have caused them have been varied. All, however, have come about because the people who have joined the movements have felt that the people in power have been abusing them and depriving them of things they deserve.