good economic conditions? Lol, the mining sector was dead from 2013 to 2018 and we had large expenditures from Rudd/Gillard years. Due to better mining conditions from 2018 we were on track for a surplus in 2020. That's all it is mate, it's not complicated. Good commodity prices = surplus, bad commodity prices = deficit. yet for some reason Rudd/Gillard never delivered a surplus despite strong commodity prices.
Your charts must be upside down or something but facts do not care about your leftie feelings. a mining giant like BHP does not crash to $12/share if conditions are good mate. Give yourself an uppercut mate