Statement (blindingly obvious)
...Trident nuke subs are hackable, thunders Wikipedia-based report...
No Shit, Sherlock!
ALL computer gear is 'hackable' if you are allowed to imagine any pre-conditions that you like. It's also subject to bugs, hardware failure, incorrect data input and good old human error in interpreting the output. And many more possible threats.
The sub itself is subject to damage or destruction from enemy action, navigational or seamanship error, system failure, corrosion, mutiny.... - the list is endless, including obscure accidents like getting struck by a meteorite.
Wake me up when they have invented an object which isn't subject to any threats at all. The issue is what you do to counter the threats, not that they exist. And I'm guessing that nuke subs:
a) have security policies and procedures suitable to prevent attempts to hack their computer systems
b) are certainly not going to tell the world what these are...