It is not known what prompted the move en masse, however, it may be attributed to economic necessity after the closure of Mt Bischoff underground mine in 1914.  The situation was dire that the miners were willing to work for half wages, but it was not to be.
Four hundred men were out of work, most of whom had built their homes on Crown land in Waratah, which had taken up all their income. While the men had been underpaid for years, the shareholders received over two million pounds in dividends and were now dipping into the reserve funds intended for the development of the mine. The Government tried to intervene not only with the propping up of the company, but also by proposing a legislation to prohibit reserve funds being used for that purpose.
The company maintained its position saying that the mine could not be profitable owing to the low price of tin.
The Government then turned to every resource to help the men, one of which was to initiate the Waratah to Wynyard road project at wages twice as much as what the men were earning at the mining company. The project was a temporary relief measure at least until the tin price improved.
The mine did not reopen and the population of Waratah decreased dramatically.  Waratah became one of the few Australian towns that experienced the greatest average annual decline in population in the first half of the 20th century. 
 Surface mining continued until 1929 before the company finally closed its doors
 The mine was nationalised in 1942 to support the war effort but was closed again in 1947
 Evolution of Australian Towns: Department of Infrastructure and Regional Development (2014)
Below is an overview of Waratah’s population for the years 1901 to 1954: