He was never stupid. Just unaware because he doesn't know the difference and ML or anyone didn't teach him how to know the ghost from living person... He is trying to figure it out on his own, now that he is a bit more aware and really starting to believe in ghosts.
Still to him... Those ghosts most of the time doesn't look any different from normal people to him. We can see it because it's shown to us, but to him it's a normal person.
If someone has been constantly thrown into deep end of the pool without any idea how to swim, or awareness what way is surface of the water and what is the bottom, they're going to die multiple times before any self-learning is even possible.
The only mystery is that how he survived this long? Maybe his energy grew while he became older, and it wasn't that bad as a child. Or maybe he had an accident and died for a couple of seconds and that really fully trigger it? Or maybe ML's shaman family put a seal on it because they seem to met as children and it broke?
??? When I said "if the plan is stupid and it works, than (the plan) it's not stupid anymore" I never called MC stupid. I was talking about how his plan of calling the other person dick etc to get his attention, though sounds silly and insane, it still worked? Hence, it's not a stupid plan?
If the plan is stupid and it works, than it's not stupid anymore - mc probably?