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.
No one has fault of what happened other than yourself but this should be more of a lesson than just a blame; you just became greedy of your bets. Concept of gambling is that you either win or lose, without assurance. Given this idea, why would you be betting all in if you're not sure that you'd be winning? If you lose then you're not lucky in that bet, as easy as that. Manipulation exist but not to all platforms and all instances 'coz that would simply ruin the platform itself. Just accep that you lost that bet and that you should not do such thing again to bet an amount you won't be fine losing. Anticipate the possibility of losing to at least restrict yourself from putting that much in a single bet. There are other people losing bigger money than what we usually engage, there will always be however if it is 'all in' on your end, then that makes a difference. We have different risk tolerance and as a gambler you should know yours.
I feel you. It;s natural to feel disappointed after a loss. I actually sometimes ask the same question on myself when I feel frustrated about the result of the game I didnt expect to come out as expected. Which later made me realize that wins and losses are part of the game. And in order for me to not feel the same thing again, I just set a budget, gambling with what I can afford to lose.
The right thing to do in all instances. We will never have control of the outcome in every bet. But I guess it would be better to expect the worse simply because this is gambling we are talking about. Regret indeed is a common response after a loss but that won't make things better on your next bets; either you become frustrated or hopeless.