From Quiggin

On the politics, I imagine that the scenario that Rudd is trying for – one that leaves him on the verge of being incapacitated by uncontrollable drooling – is that the Wong/McFarlane talks come up with a compromise that Turnbull has to take to the party room, which rejects it by a large majority. The bill goes to the house, Turnbull and McFarlane and a few other Liberals vote with the government but the bulk of the party doesn’t, and Turnbull either steps down to let Minchin or Abbot become leader, is bounced to let Minchin or Abbot become leader, or goes to the election as a weakling who can’t speak for his party. All of these outcomes result in Labor winning a thumping majority and the right coming to power in the Liberal party, and thus explain the actions of both Rudd and Minchin.
And the near-neutering of the bill isn’t a bug, it’s a feature.