is it really about mateship and security or is it about greed and looking out for ourselves?
As with all human endeavors, it's a mixture of all these things and more.
China is powerful, and its power is growing. It's going to be a major factor in regional and global policy for centuries to come. Decisions made today will be remembered by future generations. The Australian government has a lot of competing values to consider and balance as best they can.
It's possible that this decision is every bit as wrong as you claim, but I suspect there's more to it than that. Everybody puts up with China because nobody is in a position to act decisively against China. And China exploits this situatin ruthlessly every day.
It's possible that the Australian government is doing everything it can for Taiwan, short of sabotaging its own long-term survival, but that its hands are tied on this one. It's also possible that Taiwan has received private assurances of Australian support. It's possible that Tawain itself suggested this move, as a way to appease China and buy the two nations more time to perfect their joint policy in secret, before openly antagonizing China.
At a time when China is promising war against Taiwan if it attempts to finalize its independence, Australia must tread very carefully along a knife edge. A lot of important things hang in the balance, and you might do well to consider all the angles before criticizing very difficult and complex decisions.
Speaking of selling uranium to untrustworthy states, what's your take on the Iranian nuclear program? Peaceful power generation, or atomic bombs with "Death to the Jews" stenciled on the outer casing?