Can't move hierarchy to collection or parent in outliner


I have this one chain hierarchy in my outliner and it doesn’t move to the collection when I parent it to an object in that collection. Even if I try to move it manually it just stays there outside the specific collection in the Scene Collection.

Here I have a collection FISHING BOAT and an empty that serves as a parent for all the parts. When I try to parent the chainlink hierarchy to the empty or move it to the FISHINGBOAT collection, it just stays outside.

What is happening here? :face_with_raised_eyebrow:

Thank you very much in advance for any ideas or insights!