There's multiple reasons why this happens, but I'll name 3 of the most important ones.
1) We're unorganized. The masses of black people not just in Ferguson, are unorganized and do not move as one unified force. Everything we do, we do as individuals and not as a group which makes us weak and easy to destroy.
Point me to a weak nation and I will show you a people oppressed, abused, taken advantage of by others. Show me a weak race and I will show you a people reduced to serfdom, peonage and slavery. Show me a well organized nation, and I will show you a people and a nation respected by the world.
2) We're unconscious. The masses of black people are asleep politically. We know something is wrong in America, but we are either afraid to say it or just don't know the words to say it. We are not conscious of the fact that politics, economics, and education are paramount to our advancement as a race. And because we are not organized, we have no way to bring the unconscious Africans into consciousness.
3) We have no institutions. Because we have been mostly unorganized and unconscious, we haven't built any long lasting institutions that we can use to promote our agenda. No schools, think tanks, political parties, etc.
Eventually black people need to realize that unless we get serious about this problem called white supremacy, we're going to remain in the condition that we are in. Nothing I'm saying is even remotely new. It's been preached by Dr. Claude Anderson, Kwame Ture, Malcolm X, and Marcus Garvey.
The main problem has never been what do we need to do. It's always been are we willing to do the necessary work. Sadly most black people (including the conscious ones) want to take the path of least resistance when it comes to fighting white supremacy. It's why we flock to social media to be "activists" instead of going outside into our communities and getting shyt started.
If you want to fix the problems we face, join an organization and take on a leadership role. There is a humongous need for black male leadership, but not nearly enough people who actually want to be leaders.