Lynda Obst says that the "word around Hollywood" was that Inception would be only a minor success. Too weird, too hard to explain, etc.  Then the PR team took over and made it into a Movie Event. In her telling, here's how they did it:

They turned Chris Nolan into a star—not a movie star, but a cinema star. No director had accomplished this, except Spielberg. [...:] The materials cut by the WB team were taut, dramatic, consistent, and told a narrative:

1. This is an event.
2. This Director...