Casimero deserves to have a bigger fight, or a fight with Inoue to be specific, he is just trash talking so he can get the attention of the world that he exist as a champion and that they should watch him fight. It's just a strategy on how to increase the sales, we know that Casimero does not sell fight more than Inoue can, and that's because Inoue is working with a great promoter which is Bob Arum.
Maybe sales is priority but in an unification fight, regardless of the sales and the hype, both champion should meet at the ring to unified their respective titles. It's not about with the sales but the fight should happen no matter what. Bob Arum influence also a big help that both boxers no need to trash talk and the fight will be profitable by only his actions.
I guess at some point, when there's no more opponents in the line for Inoue, regardless of sales and hype, this two will have to face each other. So it's really unavoidable in their career, as they are both on the same division, has the belt (assuming Casimero will win against Butler).
Bob Arum is one of the best managers in boxing, he knows how to set up a fight that will generate money. So the Inoue vs Casimero will be profitable for him so it's just the timing on when to have this fight.