User blog comment:KillRoy231/SPOILER's return/@comment-3169324-20181130110850/@comment-77.185.190.161-20181130175646

He may still have some (or all ?) of Jack's grace unknowingly left in him.

Also, there is always a link between a vessel and "his archangel". What Crowley did to Nick might have amplified this.

But either way, him being able to awaken Lucifer will be explained as a prayer/ pure power of will from Nick. If it is, it would mean Nick's will power is stronger than Dean's who was never able to awaken Castiel in the empty on his own.