The most likely cause was the owners of the ship skimping on maintenance.
That is much more likely than the Russians or other terrorists causing it to crash into the bridge. And apparently, the bridge protectors were not up to the task.
High chance. Who needs terrorists when you have business school grads running things?
Transportation used to be run by engineering school grads and people who had worked their way up in the system who generally put safety and maintenance first, knowing it was not only safer, but cheaper in the long run.
Now aerospace (airlines, aircraft manufacturing) and about everything else is run by business school grads who only look at the next quarter profits and look at maintenance as overhead.