In a way it's a bit of an odd decision. On one hand they believe he hasn't done anything wrong yet on another still inflict the same punishment he would have got had they decided he had done it.
At the same time it seems like the decision has been reached by both the club and Mason Greenwood. It may be that they have seen the reaction by parts of the fanbase and felt it would be to difficult for him to continue. I personally have issues with bowing to fan/customer pressure because it's difficult to gauge a truly accurate representation, particularly off social media platforms but that's another debate for another day.
All in all, as I have said all along, I will respect whatever decision is made because ultimately, those that have spent considerable time investigating have made their decisions based on far more than we know.
People will point to the video and audio, they will argue the semantics of dropped charges Vs innocence but for me it's a case of reasonable doubt.
Most importantly though, hopefully the two of them can move on with their lives.