You’re mistaken in how Citadel is using math to make money. It’s not trying to decide which way a stock or bond is moving. It’s a market maker - at anytime someone can go to them and buy or sell an instrument (when no one else might want to take the other side of the deal). Citadel is using math to create the price, decide how much inventory it should keep and create hedging strategies so that it makes a profit however volatile and whatever way the market is going.