How could turbo-electric drive be more efficient than directly coupled turbines?
Short answerIt was not more efficient in power conversion; its advantages were machinery placement, shorter shafts, space use, and protection.
NotesTurbo-electric transmission did not beat direct geared turbines in energy conversion efficiency at the time. Its advantage appeared at the level of the whole ship rather than at the turbine itself. Electric motors allowed shorter propeller shafts and reduced the extent to which shaft orientation dictated machinery placement. Generators and motors could be separated, distributed, and enclosed where armor and internal volume served them best. That freedom could improve protection, redundancy, and packaging even while the machinery remained heavier for the power delivered.