The reports now indcate a distress call by the ship's captain to officials slowed and stopped traffic onto the bridge enough to save, at least, some lives. It appears six people died when Baltimore's Francis Scott Key Bridge collapsed after a cargo shp, the Dali, hit a support section of the bridge. It also appears those six were workers doing routine work on the bridge itself. The vehicles seen on sonar may be their work trucks.
In accordance with Maryland state law, cargo ships in and out of the port are required to have a Maryland licensed captain take the vessels in and out of the harbor. This offers boats captains familiar with the harbor and docks to safely control the entry and exit. However, little can be done when a ship of that size loses power or suffers some other failure. That stated, some are not so sure there was a licensed harbor boat captian in charge. Additionally, there is a possibility the ship's controls were sabotaged in a cyber attack.
In this video, a shipping expert offers a clear, concise explanation of the catastrophic mechanical failure onboard the ship which led to the disaster. But, that's all.
However, not everyone is convinced the source of the power failure was accidental. Investigative journalist Lara Logan has written about it here. Logan wrote, in part, on her "X" page: Multiple intel sources: Baltimore bridge collapse was an “absolutely brilliant strategic attack” on US critical infrastructure - most likely cyber - & our intel agencies know it.