Easter eggs?
When Connor got into Lizzie's room was it...a Liam Neeson photo with her? Like...is he her father? Which would explain why he's the monster and why he came with Connor when she died. 😮
we have to assume Lizzie was young when her father died and that tree was where they played so after he died, he felt like she was with him in the form of that tree as a monster.
Life is a joke, but atleast its a good one.