After the unpleasant turns of events, the demons returned to one of the islands occupied by their fleet.
Despite a lot going on with the demon race right now, they still didn't back away from the Fiery Hell Secret Realm because of the Spirit Fire. In fact, no one does because the Spirit Fire was just as important as capturing the elusive thief.
Not to mention the three races have been planning for this event for a century. So, nothing changed except the demons getting robbed of over a hundred original slots because of the Demon Ancestor's predicament.
If it was just a matter of the demon race's grudge against the Sky Stealer, then they won't have to compromise so much, but the thing was, it was far more than just that, so they had to pay the price for asking everyone's cooperation.