Why Do You Want Him? song meaning

This is Armstrong's first song, he wrote it at the age of 14. This was his way to express his feelings about his mother's new partner - a person that he and his siblings had a strong dislike of.
The author believes that his mother is obsessed with this man, while he doesn't care about her that much and hurts her with his indifference. And so the author is asking why she still wants him when everyone else has already realized that he's not worth her tears or even her attention.

Another interpretation involves feelings of the author's mother towards her first husband - a love that she lost. She can't forget him, "his memory will always dwell" and she still cries over losing a person she truly loved. And now that she has this new partner, she's wondering whether it's okay to fall in love again, whether it would mean betraying her love towards her late husband. And when she decides to dive deep into this relationship she drowns her sorrow in it, gets blinded and might not see that this person she is now with is not as good as he might seem.