At least in small craft, bow thrusters are usually electric, with local batteries charged from the main engine room. I don't know what large craft are like, but it doesn't seem unreasonable that a bow thruster may remain operable even if the main engine fails. Clearly that's not required or they would've had it and used it, but it could be required if the regulations didn't suck.
Furthermore, steering could absolutely have an electric backup for the hydraulic pumps that power the main steering gear. As long as there's some forward speed through the water, the rudder should work. But again, backups clearly aren't required or they would've worked here.
Steer-by-wire cars are required to have all sorts of redundancy so they're almost as safe as steering-shaft cars in case of an engine failure. This is a 9,900TEU ship with a 41480 kw powerplant. That a ship with so much more destructive potential is allowed to operate without the same level of redundancy as a $90k Audi, is unconscionable.