Might a defeat at Marathon combined with a destruction of Athens result in a renewed Greek colonial push? Citizens of other defeated/conquered cities moving to Megale Hellas in Sicily and Italy and perhaps farther west, like the coasts of Liguria and Gaul?
With more manpower, there might be a true thalassocratic Syracusan Empire.
With more manpower, there might be a true thalassocratic Syracusan Empire.