A city [Dublin] that was once host to over 30 breweries was now reduced to one. Guinness was so dominant in Ireland, that when it started its first advertising campaign in England in 1929 it felt it was a complete waste of money to spend anything in Ireland. Consumers either drank its beer or gave up drinking.
According to the “History of Guinness Advertising” it spent an average of £10,000 per year on marketing in Ireland between 1929 and 1959. Part of the Guinness strategy was whenever a small brewery closed or was bought out by it, its sales representatives were sent out to buy up all the memorabilia/posters etc. from the pubs that were previously supplied by that brewery.
In that way it could remove the history of that company from the popular imagination. Stalin employed similar tactics in Russia after the revolution, by removing people from photographs who had fallen out of favour with the new regime. Their history could be erased and they no longer officially existed. With Dublin reduced to one brewery, Guinness set about cleaning up the rest; Smithwicks & Co in Kilkenny, and Macardles in Dundalk were bought out in the 1960s. Beamish & Crawford, and Murphy’s in Cork only survived due to both of them having large tied estates in the Munster area.