This is completely normal for his age.
It’s a series of facing fears and overcoming them in a Safe way.
To learn that monsters aren’t real you have to face them
Each monster you face and overcome is a victory
It’s a process. These popular monsters on YouTube are a common part of the collective debunking that their generation is going through.
If you look at some of the lore that comes with Five Nights at Freddy’s and the new one – huggy-wuggy I think – it looks gruesome and bloody and scary and poopy
People can get obsessed with the SCP lore for years and years.
There are no secret government Labs with creepy alien monsters.
It’s Collective storytelling on the internet.
I’d like to say the target age is between 11 and 14 but really all ages explore this a little
But they also know it’s not real, even if it gives you nightmares
You still have to reassure them but you mostly have to reassure yourself