Anchors make poor emergency brakes. The New Carissa was driven from a dead, anchored stop by storm winds.
I've been thinking that since this story broke, in addition I understand it's a very sandy bottom in the area and the ship was doing 8 Knots considered fast for the size and position. A ship of that size might take 2 miles to stop.
Also seeing the black smoke pumping out just before hitting the bridge I'm assuming they were full throttle reverse, the black box exam should prove that.
As far as I know these big ships have an engineer whose sole job is to audit and work the electrical systems. Haven’t heard a thing about this guy. If there was an electrical problem he’d have known about it.