That's great, kk. I can certainly see where less exposure to caffeine would bring down BP. I don't believe there is any evidence that caffeine raises BP permanently, but it certainly can have a transient effect.
Another possibility: I can see the body simply being temporarily relieved of a task of digestion bringing some relief.
BTW, there are a relative handful of physicians who are prescribing fasting for hypertension. Now, I still do not subscribe to the notion that the reason fasting is so wonderful is because it 'detoxes' the body. I think it's more boring than that. Ex: when hypertensive people go on lengthy fasts we see two things: (1) BP goes down and (2) they lose a significant amount of weight.