The movie is pointless, about historical accuracy sometimes questionable and beside that, Stauffenberg and his Comanions (there have been quite a few more involved with important tasks) are overrated. I suppose for the following Reasons: 1. from all the attemts made to assasinate Hitler it came closest to a success.
2. makes the Wehrmacht look a bit better (as the Wehrmacht commanders where mostly quite supportive to Hitler). 3. many, if not most other attempts have been made by communists and other groups from the rather left side. Not very popular in the pre war western countries.
And keep in mind, if he had been successfull, its doubtable the outcome had been something even slightly democratig. We most likely had have a military dictatorship than.
And, in 44 neither the western allies nor the russians had agreed to any contitional surrender anymore. There was just no reason for it.