I can't speak for the previous government, since I was an outsider just trying to make the previous government act, but as I understand it, the reason for the delay was parliamentary mechanics. His private member's bill didn't have the proper lottery number or some term that you use here. In other words, he didn't have the moment in which he could actually present it to be considered for a vote, so he chose a secondary route.
I feel a little embarrassed speaking for Irwin, who's sitting right here. He could probably explain this better than I could.