"What about Satan wanting to lessen the influence of the Church?"
What about Satan using powerful people to lessen the influence of the Church?
Satan is just using humans to do his work. Sometimes they realize it, sometimes, they don't.
Folks who are actively pushing for homosexual marriage are doing Satan's work, and they know it. The average folks who support it because they think it wouldn't be 'fair' not to, are doing his work, but may not realize it.