With the new ratings system Classic Hit stations tend to do better (ie no real change but they appear to be doing better than once thought). They saw how Magic went crazy from a 2.7 its first month to 5.4 ratings share in about 3 months and wanted a piece of that.
One month after the Wave Change Wave is up one point (6.1 I think) and Magic is down 1 point (to 4.4). Its interesting to note Magic lost ~30,000 listeners and the Wave gained ~30,000 listeners.
But why is a good question perhaps they miss doing Oldies (as Oldies 92-9; The Greatest Hits of the '70s and '60s) and this is a second try. Or for whatever reason they wanted to take the heat off 101.3 2WD who had suffered in the ratings. (Now they are the only Soft Rock/ A/C station).