The concept of gambling as a form of mental sports refers to the deployment of mental strength in some skill-based games and without physical display of strength or fitness.
Except on the big difference that gambling involved money so mostly you are playing for the sake of winning your bet rather than the simple glory of winning the game on sports.
Also, skill based gambling usually still have some lack factor to win the game because analysis can’t be 100% accurate unlike games like chess that result can be calculated.