They're looking to counter Chinese moves in the South China Sea in particular, as China has been acting aggressively diplomatically and economically towards Aus

They're looking to counter Chinese moves in the South China Sea in particular, as China has been acting aggressively diplomatically and economically towards Australia under Xi. The advantage of nuclear subs over diesels is the long linger time while submersed, and the range. So I think Australia is wanting to do a little force projection of their own.