Why did that tequila brand change distilleries? Well, it happens, right? I mean, Cazcanes, they changed distilleries. Pasote, they changed distilleries as well. And Majenta changed distilleries also. And several more.
So here are five reasons why that might happen. First, capacity issues. The brand just outgrows the distillery's ability to make enough tequila. Second, the distillery focuses more on their owned brands, and they add a lot of other new brands that they have to support. Third, inconsistencies in quality, or maybe even disagreements over flavor profile and the style of tequila being made. Fourth, you might change distilleries because of cost. Brands might be able to make their product less expensively elsewhere. And fifth, the brand itself may have been purchased and then moved to a new distillery; Casamigos, for example.
Tequila is, after all, a business and changing distilleries doesn't inherently mean the tequila brand is getting better or worse. It just means that everybody made a business decision that they think is best for them.