Seen Dune2 now.
What the everlasting fuck?
There are two, very simple, main plot drivers in the book:
1) The stability of the empire depends on mutual mistrust between the great houses, pinned in place by the Emperor having the best army (the Sarduarkar). Duke Leto upsets this by creating an army of equal, if not better, quality than the Sarduarker. Hence the Emperor plots to remove him from the scene and destroy his army.
2) The entire civilisation depends on the Guild Navigator's ability to 'fold space' and hence provide transport. The Guild Navigators can only function with spice; they are all failed, limited versions of Paul Atreides. Hence, when Paul controls the spice, he can blackmail the Guild, and they tell everyone else to fall in line and bow to Paul.
So, why, given these are simple, and could have been described by the plot device of having the emperor's daughter dictate into her diary, did the director completely abandon them?
Makes no sense, unless they are going for a 3rd film that completely departs from the books and wraps things up in a messy, non-canon, way.