Expect the unexpected is a thumb rule in sports, it maybe fixing or just happened as coincidence which is the reason why we should not be relied too much into the favorites in sport betting.
I don't think this was match fixing because Argentina didn't play like a team that wanted to lose that game. They played very well and if it was any other day they would had won that game but it wasn't just their day as all their open play goals got cancelled for offside. There was even a goal that was meant to stand as the player been used to determine the offside wasn't meant to be used since there was another playing keeping the Argentina player on side.
The Saudi Arabia team also tried their best as their defense was quality keeping Messi out of possession and not allowing him time on the ball to carryout match winning passes as he usually does.
We never know if the game was a result of match-fixing since both teams will surely act accordingly if the game is rigged. They will definitely make it look real so that audience will not cater any doubt on the result. Any team can make it look like they are trying to win but always miss whenever they are trying to get a goal or something with the same intent.
If ever the result is legit, then I believe Argentina had been outperformed by their opponent. Maybe the strategy their opponent implements is somehow hard for the Argentinian team to counter and as a result, Saudi won, we also can't remove the possibility of the Saudi team getting lucky.
Argentina is a big disappointment, It's still hard to believe, I quit betting until I am able to forget this experience entirely.
"All in" is usually a mistake. No matter what, surprises can happen. What would you expect, after all?
If it was money you afford to lose, I think that as soon as you get other money you afford to lose you should bet again, even small amounts, to keep the games more exciting.
Of course, this is an idea; all is up to you. I really hope you've lost only money you did afford to lose and the amount was not
that big...
It is indeed a huge mistake but a bettor that has full confidence in the playing team will surely go all in just like what @OP did. Somehow I think @OP forgot the term upset.