Only those rich bettors would get inside information if indeed it's rigged, but it will not be announced in the public as it will destroy the reputation of the sports or game. Lucky are those who have the knowledge as they can make an easy money, but like I said, you need to be rich as this info is not available for ordinary people.
Maybe it wasn't your intention, but you sound like rigging happens all the time and rich bettors take advantage from knowing some inside info. It could be the case in the past, like decades ago, but now game-rigging in sports happens very rare, especially on the high level. Some local, unknown to the rest of the world events can still be rigged, but the higher the level of the game, the less probability of it being rigged.