As you said, they humor these guys because they have connections to big money in the middle east. No big surprise there.
Again, it's not just one month. Ankalaev last fought during Ramadan in June of 2017, but since then he hasn't even fought until months after Ramadan. This is the trend. More and more fighters observing Ramadan are not only refusing to fight during Ramadan, but refusing to even train during Ramadan. They want 2-3 months afterwards for training camp.
I'm sorry but it's insanely unprofessional to be an MMA fighter and refuse to fight for 3-4 months of the year because of your religion.
And to add onto this point: If Umar came out and said "I will fight Merab in January, Febraury, April, or May, just not March", I don't think we'd be having these discussions right now. And the UFC certainly wouldn't allow Merab to duck Umar by only fighting during March (they would just not offer him a fight that one month). That would make it impossible for Merab to duck him. But Umar won't fight in April, because he won't even train in March. That's Umar's fault for being unprofessional.