It actually can be explained, it just shouldn't have to be.
To put it in a very small nutshell, government policy is the reason for these protests. Be it the wars, bail out's, immigration reform, the police state, unemployment etc and etc..
Also the problem with the movement is that it has no leadership, so lot's of people attached themselves to the movement that have causes and reasons to be there that had nothing to do with the original intent of the movement.