Why histories shifted blame onto the Royal Navy

Was the tendency to blame the Royal Navy for Coastal Command's weakness created by air-power historians?

Not entirely; some historians repeated contemporary sources that shifted responsibility away from the RAF.

The interpretation cannot be reduced to later air-power historians. Some authors followed period sources that found it institutionally easier to blame the Royal Navy than to acknowledge weaknesses within their own service. Later histories can therefore inherit inter-service advocacy from the documents they use.