Crown Colony cruisers as war-build Towns

Why did Britain build Crown Colony-class cruisers instead of more Edinburgh-type Towns once treaty limits were fading?

They were intended as faster, cheaper war-build Towns that preserved most of the larger design's capability.

By 1938 the treaty framework was weakening, but Britain still needed more cruisers than its yards and budget could provide. The Crown Colony design retained much of the Town class's fighting value in a smaller hull suited to wartime series production. Its intention is summarised as roughly ninety percent of the capability for seventy-five percent of the cost, although the actual savings were less dramatic. The choice concerned fleet numbers and construction tempo rather than ignorance of the larger Edinburgh design.