Kennedy could not pass it because he didn't have the support of the congress who was mostly conservative at that time. When Johnson came, the tides shifted due to Kennedy's assassination and the general mistrust in the government and contempt for the Vietnam war, so it was easier for Johnson to get the support that he needed.
A collapse of their newly independent nations. Although the diverse ethnicities were unhappy under the Austro-Hungary empire, they were secure under the government.
