Not sometimes, but all the time the game of football is unpredictable and the same as all other gambling games, most people thought Argentina will have a slide win in the match against Suadi Arabia but the outcome of the match was different and most gamblers got the tickets destroyed with just that one game.
Similarly, the game between Cameroon vs Brazil also is one game that got most football speculators off guard because most people gave Brazil straight winning in their ticket.
Yeah, there are lots of factor that can affect the result of football. It isn't only the players' skill (though this plays a huge part) that dictates the result of the game, game strategy, conditions, opponent skills and strategy, the audience have also a huge impact on the game. That is by ordinary means of the game output but sometimes, there are an unknown factors that can turn the result of the game such as fouls, warnings, disqualification, player being thrown out of the game etc, that also contribute to the behaviour of players that affect their ingame capability which can result in poor performance and worst the team defeat.
Many times people ignore how powerful the impetus of having the audience in your favor can help the players to perform way better than what they can usually do, during the match of Argentina and Saudi Arabia a great deal of the people there were not Argentinians but they were supporting them mainly because of Messi, however as soon as Saudi Arabia tied the game the crowd flipped and began to cheer for Saudi Arabia, and once they got the lead the stadium went crazy and supported them until the end of the match, showing how what happens in the field and outside of it can create a positive feedback and create amazing results.