But considering the source, it's pretty understandable. A gentleman in 1904 is writing a lullabye. He sets the scene of mystery and ancient Irish beings. He's evoking the beauty, mystery, and awe of Lough Gartan. But it's a lullabye, which means that by the end of the song the child should be lulled. He's also from a time and place where there's a dominant faith perspective- Christian. So he concludes the song with a peaceful, lulling scene that brings the song 'round to the dominant world view.