Why is this always a question?
Guys, this is a high-profile murder case. Do you realize how hard it is to convict a cop who's job inherently involves the use of force? It's not as clear as you think it is and a prosecutor has to do everything within their power to facilitate an air tight case.
What if the Minneapolis PD actually trained cops to use the maneuver that cop used and encouraged them to use it? I don't assume this is true but what if they did? That changes the charges right? Well, it takes time to investigate that and understand the situation. You simply can't rush things and overcharge a suspect or they walk free.
Why is everyone always in such a rush? Calm the fuck down and let some very smart people do their jobs thoroughly so the outcome is the best it can be for everyone. If you rush a murder charge, it's a good chance the guy walks.