Thamel earned its role by accident of geography and momentum. It sits close to the airport, close to Durbar Square, and close enough to everything else that decades of trekking outfitters, guesthouses, and bars simply piled up on top of a much older neighborhood and never left.
Mad honey is reported to produce a mild euphoria and body warmth. In larger amounts, it can drop your heart rate and blood pressure hard enough to put you in an emergency room.
What happens when Buddhism runs into religions that didn't grow up next to it, the Abrahamic faiths and, at its own root, Hinduism. Some of these encounters produced quiet blending that lasted centuries. One produced an entirely new religion, deliberately engineered to contain them all.