A few podcasters have pointed out that Robbi and Rip very blatantly slowplayed each other in an earlier hand.
Both had AQ, and both flopped trip aces. Yet they put basically put little or no more money in.
That is possibly the clearest evidence so far of them colluding, and furthers suspicions of what else they may have been up to. Combined with them not disclosing their backing arrangements, it at minimum suggests they are unethical players.
This is one of the reasons that that Robbi and Rip are suspect, not to mention that Rip is professionally affiliated with Jake Paul, who's a confirmed piece of garbage. Like folks have said, being unethical/colluding does not mean you cheat, but it increases the likelihood.
Of course, very few folks playing casino poker are what I'd call moral beacons, so I wouldn't go too crazy with it. And even relatives/friends will slowplay in that setting. I remember a hand at the $2/$5 NLHE game at Lucky Chances where two guys checked down a hand three streets and the IP player had a set on the flop with a dry runout. Someone complained, and the IP player just smiled and said, "Hey, he's my cousin!"
My first impression was likely cheating, after hearing Robbi change her story multiple times it increased to high likelihood of cheating, but after rewatching the hand some more, I'm now leaning towards more likely her being nutty and cheating not likely.
It appears Garrett doubled down on the cheating accusations post stream. He's not infallible, though, and actually based on his poker expertise, more susceptible to certain cognitive biases than average players like myself, not to mention lay people. Also have to factor in the recency bias of the Magnus accusations in chess and the Postle situation a couple of years ago. Someone that's played a bunch recently with Garrett even had his own cheating accusations discussed on this board in the past year or so
For Garrett's sake and Robbi's, I'm hoping that if nothing turns up he makes a big, public, heartfelt apology and returns the money. Actually, I think he should do as some have suggested and put the money in escrow right now.
That said, I have a lot of respect for Garrett and his intuition. I've watched him play in a lot of streams, and this episode is very uncharacteristic of his reaction to losing big hands, even to obnoxious players. He was there (with a lot more inputs than I have watching an edited stream), and it wouldn't shock me if he turns out to be right. And if he is, I hope all the folks calling for his head give the man his props.