Usurper Victorious results in the conversion of the Usurper mobile units to their Imperial side. Remove the Imperial leader whose leader value was applied to the die roll and replace the Usurper marker with a random leader. If Usurper units are flipped to their Imperial side, the System unit is also flipped to the Imperial side if it is on its Chaos side. Roll the indicated number of dice and add to the Chaos Index (representing the additional chaos resulting from the changing political space-scape, new policies, alliances, confusion, etc.).
Why are Usurper units being flipped to Imperial units if the Usurper wins? What am I missing?