I thought the film was about how Obi-Wan seized upon the opportunity that the Death Star crisis presented. Obi-Wan's true motivation (and the true plot) of the film was to get Luke "Involved" with the rebellion, and therefor into a position where Luke could become the "New Hope" of the Jedi Order.

In fact, it was never intended that Obi-Wan would have anything to do with the plans beyond delivering them to the Rebellion. They did not even know what the droid was carrying. The main drive was Obi-Wan's snaring of Luke to be a Jedi. That Luke decided to Join the fight and blow up the station, was not the main objective. It was that Luke had become Force sensitive as a result of his involvement in the battle and blowing up the Death Star.