If the price is guaranteed to rise significantly after the halving, why aren't you buying as many coins as you can now so you can make a guaranteed profit when the price rises? Why wouldn't the smart money buy up all the cheap coins now, up to the post-halving price, and therefore pricing in the halving jump in advance?
I put it to you that this has already happened.
Because small traders are agile traders that have advantages in markets. If someone is a billionaire, they're not going to go all in on Bitcoin because...they aren't going to go all in on anything no matter how good it sounds. You have some rare exceptions like Soros, but he's an insider trading financial terrorist benefiting from government connections and should be in jail.