Or trust limiting, a duopoly or oligopoly instead of a monopoly?
Speculating on alternate historical outcomes obviously proves nothing, but I personally think a great many of the American breweries that were extant at the start of prohibition would have survived the economic and political upheavals of the thirties and forties if they hadn't been forced by prohibition to suspend their business activities for more than a decade. The reason Coors, Bud and the other giants survived, albeit as mere shadows of their former selves, was because they were so large that they had other niches to exploit. IIRC Coors relied heavily on Coors Porcelain while also producing food items such as malted milk powder. In some ways it was almost inevitable that the survivors of prohibition would become giants that dominated the market after the war, the bar to re-entry was too high for most little guys, both in terms of capital costs and in terms of recruiting experienced help - when an occupation is banned for more than a decade the people who formerly plied the trade must move on to other work. What wasn't inevitable was how long the biggies were able to own the market.