I thought Poker was a game of understanding your opponents not only based on past actions with cards but also by looking at facial expressions, body language and determining whether or not they have a good hand. Along with that, a big part is developing subtle gestures to throw your opponents off.
Reading body language only works with really bad players.
What modern poker AIs do is play 'game theoretically optimal' (GTO). If both players play GTO, then it is a draw, but if your opponent deviates from GTO then your GTO strategy will beat their strategy. If you are playing 'bad' players you can deviate from GTO and win even more than the GTO win rate (this is called exploitation), but it is better to simply play GTO until you know for sure that your opponent has weaknesses to exploit that you can safely exploit.