Why do some people say that there is match-fixing in the World Cup?

As an old football fan who has watched football for 20 years, although I am only 27 years old. I insist that there are match-fixing in the World Cup and Champions League. This is my opinion, which is probably wrong. First of all, I want to make two points. I have watched almost six World Cups, and I have watched more than 20 Champions League matches before each year, so I am not fake fans. Secondly, I hardly gamble on football, and of course I have never bought it at all. Generally speaking, it is just chatting with friends and buying a few hundred dollars for fun. Of course, I have systematically considered why a game is fake ball, or the source of interest of fake ball, but I don't think it is necessary to analyze it in detail here. In fact, if you don't play tricky football, gambling will hardly flourish to this extent. I only want to raise one point today, that is, the match between two German teams, Germany vs Sweden and Germany vs South Korea. If we watch these two games, we will have a question. Why can the Germans easily crush the Swedish defense after blowing the horn of counterattack, but they can't face the South Korean team in the second half of the battle? I have reason to think that it can easily break the attack line of the Nordic people and tear open the defense line of the East Asian team in a freehand manner. I said bluntly that Germany's loss to South Korea was a match-fixing.