User blog comment:ShawnCognitionCP/The Empire vs Stormcloaks, the most likely answer/@comment-3407280-20140612232511/@comment-14027812-20140613023600

What helps the Dominion: Continued civil war > Stormcloak victory > Imperial victory

The Stormcloaks indirectly aid the Dominion by rebelling. They say a Stormcloak victory is not to be preferred because it would be less helpful than the war continuing to go on.