Probably 90% staged for publicity. The lack of security, after the incident, lends itself to the view that the whole thing was set up.
They probably wanted some oscar news coverage and used the preexisting feud between Chris & Will as a setup.
That being said, I think Will actually hit him instead of pulling his punch like they would have rehearsed it. A little truth in every lie holds the whole story together much better. π¦π©βπ»