The sentence is a little garbled. My reading of it is "Why [is] the Victorian moral project and supposed 'prudery' [not an accurate assessment of Victorian attitudes] in the first place?"
Alternately, they could be arguing that "prudery" that originates from a project of improving societal morality is not necessarily a bad thing.
The definition you propose applies a modern, negative connotation to "prude" that is certainly present in the English language, but there could also be more sympathetic interpretations of the same characteristic ("innocent" and "straight-laced" and "proper" come to mind).