It's always been this way. What's happened in the last five years is the continued expansion of videos capturing bad acts by police. The bad acts by cops aren't new, but the videos documenting it being widely available are. 

Think back to Rodney King. That incident was captured on old school camcorder. How many bystanders just had a camera at the ready back in the 90's or early 2000's? Now nearly every member of the public has one on their phone ready to capture video at a moments notice. And instead of the police having TV shows like Cops to present the one sided vilification of all police suspects through the bad actions a few, they now for the first time have to really deal with accountability to serve and protect in a legal manner.