Can somebody please shine some insight?
If I may speculate....it's not about the thumb. It could be a few things.
1. After Rousey pulled amazing PPV numbers in Brazil, UFC brass may have felt it a much safer sell for a stadium to put Rousey on the card.
2. Robbie is probably very OK with trading UFC 193 in Melbourne with UFC 195 in Las Vegas. Robbie has never fought outside the USA, that I know of.
3. Robbie may have protested going to Australia to fight an American after being headlined by a smaller weight class interm title fight.
4. If he did have a thumb injury, 7 more weeks would be advantagous for him to fully rehab that and still have a full training camp.
5. It will be summer in Melbourne( I think) and she could have another post fight vacation. There could even be an extended layover in Hawaii on the way back, it you know what I mean.
6. It also gives Rousey more time to fully recover before she starts filming
Mile 22 in February. She broke her thumb in her 16 second finish of Davis. No matter how dominant she is, she can still take some damage.
There may be some more aspects to this, but the way I see it. It works for Robbie. It works for Rousey. AND it works for the UFC.