Who has the information about their split before their supposed fight was cancelled? As we all know, they have a scheduled fight last year, April 26, 2020, but due to the effect of the pandemic, that was permanently cancelled.
I did some research regarding your question but I didn't find the exact answer, but instead this article.
John Riel Casimero might need to take reduced purse to fight Naoya Inoue, says Bob Arum
Can you believe that? Arum still wants to reduce the purse of Casimero just to make the fight happen, I think they like to rob Casimero and disrespect his status being a champion. I'm sure the purse was not 50/50 on the cancelled fight and after it was cancelled, Bob talks about reducing Casimero's purse, so I'm guessing maybe it will be 70/30 which I don't think is fair.
I don't think that was unfair.
If no Arum, the event won't become big. Arum's influence can boost ticket sales since he's the only promoter that capable of making the fight happen in a big event place. As I checked some details, the cancelled Inoue vs Casimero fight is supposed to happen on Mandalay Bay. Arum also has the power to choose a big opponent for Casimero. Arum is the key to why Pacquiao also got a big fight during his prime.
We should accept the fact that Inoue is much more valuable compared to Casimero. The former already destroys every contender that wants to take his belt so it's understandable that he will get the most bid.
Maybe it was unfair to us but once Casimero finally defeated Inoue, he's the one now who will have the most bid on his future matches. Pacquiao also experienced that before and just gained a big break after beating Marco Antonio Barrera.
The word "fair" is only based on our personal judgement, but Bob Arum being the promoter knows how to run his business and he is investing his money for the fight, if the fight is unsuccessful, he will bear big losses so it's just right that he will make money. However, if Casimero's camp finds the offer unfair, then there's nothing we can do because they won't be able to sign the papers necessary to make it happen, it's a conflict for money which is the main hindrance of this fight not happening.
I'm also with the side that Arum can't be called unfair. Arum is a big promoter and he is also spending money on the fight. If let's say Inoue will get a 70/30, that was fine because after all, Casimero is the challenger and if he won, he will be on Rank 1.
We are most PH people here that's why others called it unfair but if Casimero will fight Inoue, the latter will be the reason why the fight will be hyped and not because of Casimero. Just take it Casimero's big break once he defeats Inoue. But he needs to win first with Butler.