I'm both a big fan of beer and a big fan of history, so I've been wondering about this lately. The brewery purported to be the oldest in the world is Weihenstephaner in Bavaria, and their most famous beer is their hefeweizen, a wheat beer. The brewery opened ~500 years before the law originated in Bavaria, banning wheat in the production of beer. I read that Bavaria even required the Reinheitsgebot to apply all over Germany as a condition to accept joining the unification. So it seems like it at least used to be a pretty big deal there.
But I also read that this law was recently changed to allow for bottom-fermenting beer to be made with different malts. But there are hundreds of different brands of hefeweizens, dunkelweizens, kristallweizens, weizenbocks, you name it, many of which are made by ancient breweries like Weihenstephaner. Were these beers being made all along, or did all of the Bavarian breweries just recreate the ancient style in the last twenty years?
Good catch - it was originally banned by the Reinheitsgebot, and there was also the consideration that wheat must be reserved to feeding people. In the 16th century a guy called Degenberg received a permit to make wheat beer - it was purely fiscal, he paid dearly for the privilege and had profit-making in mind. Eventually this privilege was inherited by Duke Maximilian I, Prince Of Bavaria.
So, unwittingly, the richest and most powerful guy had an exclusive monopoly on it. invited a brewer to Munich and it became so popular that pretty much every town had a subsidiary of the princely business, generating huge amounts of income for the state.
So it seems a lot like a lucky coincidence of the population really liking it and a prince having a monopoly on it who could invest into putting up the supply to feed the demand and making a lot of subsidiary businesses.
It sounds a lot like a modern business story, when a very rich corporation has an exclusivity, like similar to a patent (here, an exception from the law) on a popular product and they really invest into supplying it everywhere.
When it became less popular, they started to sell them off and selling permits to nobles to make it.