Possibly because for, say, 140% of Gascoyne's current market cap...

Possibly because for, say, 140% of Gascoyne's current market cap plus whatever Gascoyne is paying for Firefly Ramelius would pick up a near new 2.5mtpa mill that runs on the smell of an oily rag and is just down the road from Ramelius' cornerstone project at Mt Magnet.
PLUS low grade but under explored near-mill resources
PLUS small but high grade opportunities at Yalgoo (they love the mix of low-grade near-mill and high-grade but stranded)
PLUS another project in the pipeline
PLUS about $100m in tax losses.

Not only would they get immediate cashflow from the Dalgaranga project but they the medium term boost from Melville at Yalgoo and the longer term possibility at Glenburgh.

But as Timbin and a couple of others have pointed out Ramelius might be tempted to go for something with a lot more resources.