Australia literally made public comments one year piror to the contract cancellation stating they were looking at alternative options. The contract underperformance was widely known and the actual cancellation didn't really come the surprise of anyone - the French just thought it was "too big to fail" so to speak.

Now, you might be able to argue the French were correct that Australia wouldn't cut its losses and terminate the contract if the nuclear sub deal wasn't on the cards. However, it's hardly the fault of Australia if it makes the desire to seek alternative options known and another viable option is presented.

If France cared that much, they should have dealt with the underperformance. It's like a business failing to deliver their services to an adequate standard, and then getting pissed off because the client went to another company. That's how business works. France gambled that Australia wouldn't have any other option than to throw good money after bad, and they lost that bet.