Electric-drive warships before modern hybrid propulsion

When did hybrid diesel-electric or electric-drive propulsion become viable for warships, and what did it improve?

It was viable by the 1920s or earlier; electric drive let designers connect the propellers to power generated by steam turbines, diesels, or other machinery.

Electric drive became viable earlier than present-day hybrid-propulsion terminology might suggest. American battleships already used it in the 1920s or before. Once propulsion is transmitted electrically, the generating plant can be a steam turbine, diesel, or another source. The arrangement provides flexibility between power generation and the machinery turning the shafts.