it is questionable if the cars had moved by the time it was "too late".
the tipping point on a ship that size, may not be far enough to cause "sliding" like that.
The investigation isn't complete, but yeah, they said they accidently shifted the center of gravity too high by the change in cargo.
They also left a door open that helped contribute to the flooding and being unable to correct.

It sounded like the start of fish tailing to me. Tried to go one way, over corrected to go the other and didn't center the wheel soon enough and bam, gone.
Because they were so close to shore and other ships, was the only reason they are all alive. They basically said if it had happened out at sea, no one would have known what happened.