Why interwar marine diesels reached a power plateau

What limited high-power diesel-electric warship propulsion in the interwar period?

Metallurgy and the practical power available from marine diesels were major limits, with the biggest widespread advances coming later.

The discussion describes a plateau around the early 1930s, followed by much larger advances in the 1940s through the 1960s. Exceptional engines existed earlier, but they were scarce and expensive rather than broadly available for fleet propulsion.