[robot_no_419]

It's not the opposite either. Chess is a game of skill, poker is also a game of skill.

The difference is that chess is deterministic and poker is not. Chess skill means being able to forcefully convert a winning or drawing position. Poker skill means optimizing your chances of winning.

Not only is it possible to beat weaker opponents in chess by playing the best moves (contrary to your assertion), it happens all the time over the board. Weaker players are more likely to play moves that transforms the chess game from a win/draw to a draw/loss for them. There isn't a single human or engine alive that can consistently secure a draw against every opponent.

And it's possible for a poker player to mindlessly play the mathematically optimal move and still lose. Poker IS a game a chance, so they could just get unlucky.

[im3w1l]

If we define optimal play as never turning a win into a draw or a draw into a loss, then I think it's possible to play a passive-but-optimal style, with few traps for weak players to fall into. Also if a position is "lost" but it's very very non-trivial to see why, a stupid-but-optimal strategy is to resign or move pieces randomly. You need psychology to win from a lost position.