The original emigration to SA was almost certainly due to slowdown in Manx Mining starting in 1880's - after this family pull would drag the young towards established Manx groups (after all much easier to get started if your cousin, uncle etc are there to help as seen in Cleveland - these emigrants would have little or no capital behind them) - remember that prospects on the Island were limited and post WW1 looked fairly bleak except for the very seasonal holiday trade, the 1930's were not good for steady work (The Island population declined from the start of the 20th C - in fact had been in effective decline from 1850 as many young emigrated).