Then I have all sorts of thoughts blaming casino, like do they manipulate the result of the game when user goes all in. I am sure they are all fair, it's just that the possibility of losing the game may be minimal but it's never 0.
High expectation to win push you to question if it's provably fair just because you go all in and lose. That's not unusual for gamblers to think that way, however keep in mind the risk when you started to use your money to bet. You can never be certain, the reason why we should not expect to win because losing is inevitable even in a point that you're confident with the possible result that's why you go all in.