We can say that mathematics is the structural basis of long-term profit. But that's not all, playing poker is about making decisions based on many factors, on every round, on every street, on every action, even on the same street.
Let's say you're on the button, at the start of the tournament with a pair 88 and 50 blinds, UTG pays 1 blind, MP pays 1 blind. The action comes to you, so you make a decision, based on your stack, the stage of the tournament, and your weak opponents clearing. In this case you will raise to 5 or 6 times the initial bet and play your pair in position against a few opponents. So if that opponent who cleared from UTG calls your raise and the flop comes AT5, UTG checks, you C-Bet and UTG calls, he's probably calling with an A and another low, what's the chance he's folding and you win with your hand? It's too low, weak players hardly drop an A early in a tournament. But now imagine that same situation, only this time, we're in the money bubble and you have 15 blinds, the odds are still the same, are you going to raise to the same 5 or 6 blinds? Of course not, you're going to go all in, and make your opponents fold their
hands, or when you get called, unfortunately, it depends solely on the probability of making it to the river as a winner.
I don't know if I was very clear, but in poker even online, you're playing against people, and people aren't machines, they make varied and often unpredictable decisions that not even math can really predict, and that's where the charm of poker, you defeat math by exploring your opponent's mind.