RCs in assembly halls has been predicted by many on here, especially once the move to 2 x 1 day CA events took place. Large RCs might be money spinners but they also cost big. Assembly halls are often debt free and overheads fairly minimal. I bet they have done the calcs and worked out they stand to make more through higher occupancy at the assembly halls.
The move in Australia may have additional side benefits with respect to the timing of the current enquiry but I think the primary cause is cash and not the Royal Commission. Don't forget as well that the trek to the international convention last year was not well received if my information from friends down under is correct.