The point is not that GGG is less interested, but Canelo sees no point of making a third fight against GGG. For Canelo, GGG is already a beaten opponent. If Canelo looses to Bivol, I dont think fighting against GGG will be a recovery. Some might disagree, but I think that will be a step back for Canelo. Canelo would have gained, fame, if he would fight GGG if not same year, but at least in GGG. I think GGG will box for next few years only, maximum till 43. Only fans are interested in Canelo vs GGG third fight, but not both boxers.
The fight is very controversial and for many years, Canelo has been haunted by it. Boxing writers continue to ask him why he didn't want to give GGG a third fight. And maybe he wanted to show who the real winner is but facing him in the trilogy. But we can talk about it later once he settled and win against his tougher opponent in Bivol next month.
Maybe Canelo becomes sick of everything and now finally decided to face GGG in a trilogy to end their saga. Much especially now that GGG won against Murata and added some titles on his, Canelo has no choice but to face GGG for the third time. You are right that before we talk or discuss the trilogy, Canelo should be the winner first of his upcoming fight against Dmitry Bivol. His opponent is also in his prime, the same as him. Canelo winning this fight will be the key to the trilogy with GGG but if he loses this, no more trilogy.
We should focus first on this fight before anything else. Bivol is not an easy opponent but Canelo should be able to handle him.
Canelo have no other option as well because for some reasons his fight against Ilunga Makabu has been cancelled and now that he's been offered a fight against a champion in Light-Heavyweight who also have a clean record but that deal also includes GGG on the contract and if he doesn't want to fight GGG for a trilogy then he also won't fighting Bivol. I have already said this in the past weeks that even if Canelo doesn't want a 3rd fight but he got no choice here but he is not worried because he personally knows that he can handle Bivol well and give GGG a 3rd fight before the man will retire (probably).