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There's nothing mankind isn't capable of, including this you mentioned here. So, we can't completely rule that out in sports and betting. I believe if that's possible at the lower league, it will also be possible at whatever top league there is. It's just that those at the more established leagues will be more discreet than the amateurs, knowing what's at stake and the dire consequences if their cover is blown off.
We've seen awards go to players we ordinarily believe didn't deserve them. If anything, such alleged skewed awards also point to rigging. Anything handled by humans is bound to harbour compromises. Match fixing isn't an exception. That's my conclusion.
Of course - sports can be rigged for personal gain by individuals or groups. Match-fixing, bribery of players and referees and other similar practices may still exist - but these practices are conducted in a highly secretive and structured manner. We never know what really goes on behind the scenes until it's revealed in the future, so always gamble wisely, as gambling can be a very tempting business for some.
Lower leagues are the most likely to experience such cases - but even the top leagues are no exception, as gambling mafias are always looking for ways to maximize profits. Cases like this have happened before and they certainly won't be easily forgotten - as they are now considered history.