The power switches off twice and goes on again. The power may set the steering to one side. Almost like a steering-lock in a car. Or with 2 screws, one screw standing still while the other is rotating. There are several ways how this may happen. The crew probably knows more about what happened.

The power outage is likely a power generator problem. The power of the whole ship goes off twice in the full video. This can happen when the fuel of the generator is too low. And the fuel problem can be due to theft, drinking, politics, rust, etc. Or it could be a faulty connector.

Some think that the bridge collapse could be done on purpose. The boat has its own power system and communication system. So it is probably very difficult to get to the power system from the outside. it is also extremely hard to steer a big boat via a power outage, let alone making it hit a bridge.
This could have been an internal job with a person on board. But still steering the boat would be nearly impossible, unless you do the steering yourself.