It was stuck in the Senate for half a year?

Sort of. If you look at the timing of its actual passage you can see that even though it was first introduced to the Senate in March, Labor didn't actually even schedule it to be debated until May. So That 6 months is down to 4 right off the bat.

After that, things get more complicated. Without a doubt, some of the delay was indeed caused by the Greens. But some was still caused by Labor, too. I forget the precise timeline, but circa June or July, Labor agreed to some compromises with the Greens. The Greens continued blocking the bill and arguing for more compromise out of Labor.

At the time, I was actually upset with the Greens and thought they should have accepted the initial compromise. But after talking with someone from my local Greens MP's office, I found the trick...despite agreeing on a compromise with the Greens, what Labor actually presented was the original, un-amended plan. It took weeks more before Labor finally actually presented in Parliament a Bill that they had negotiated to get Greens support on.

We are a conservative country, the Greens are currently polling within 3% of One Fucking Nation

Just looking at the latest polling, Labor + Greens poll at 47.5%, while LNP + One Nation + Trumpet of Patriots at just 43.5%. Labor are ahead of the LNP. Greens are ahead of One Nation + Trump. And if you look at the last actual election results, the Greens outperformed One Nation by more than a factor of 2.

So yeah, we're a country with a lot of conservatives. But we have a lot of progressives too. And the Greens' job is to represent the views of the people who voted for them in Parliament. That means pushing, hard, to get Labor to do more than just fiddle around the edges, as they are so often wont to do. In the case of the HAFF, it meant pushing Labor to increase the amount invested in total, and also to make sure it wasn't only a long-term project that might eventually pay off...if the LNP doesn't dismantle it first, but that it is also able to start doing good work immediately, by requiring a minimum spend instead of Labor's planned maximum spend.

Thanks for linking that article from Sriranganathan. I hadn't read it before. I found that interview he showed a video clip of particularly galling. That is precisely why I support the Greens and I have become more and more upset at Labor over the last 3 years.