As others have mentioned, Jetconnect J (or J into WLG) isn't worth the money or the points. It's hard to say why it's so full so far out, maybe there's something on during that time.

Note that with those 737s, there're only 8 J seats per flight, perhaps that explains it a bit. The timetable also fits well withe the corporate type, early departure from WLG means an early arrival in Aus, allowing a full day of work. Then, they can catch the return flight in early evening so a midnight arrival - works well for the business type.