I've actually seen this one plenty of times. Kudos for the write-up.
Just using some logic should hopefully make it clear why this is a scam. Firstly, fixed matches are illegal, and why would anyone openly advertise the fact that they are in on fixed matches? Secondly, if there were indeed a professional match fixer, why would they let anyone else know, as that would diminish their profits?
Sometimes greed gets the best of people and they fall for this. But it is entirely avoidable.
Well believe it or not there have been actual fake matches marketplaces but it was nothing like what I talked to in the OP.
For one, yes, anything advertised through social media involving gambling is likely to be a scam. META, Facebook's and Instagram's parent company, is notorious for accepting scam ads which lead people to being tricked again and again.
These will get reported and perhaps deleted but by that time the scamers don't care. They Just get new URLs, rebrand their marketing, and keep going. Or if the scam wasn't effective enough, they just create an entirely new scam altogether. It seems as though these scams are staffed by many skilled workers. Some being active in chat constantly, the websites and marketing materials being well designed and they even have support agents responding in due time for their fake websites. It's amazing. So it's easy to tell that these are well organized operations, even more organized than certain businesses I've known.