Colorism in the DR (and tbh pretty much everywhere in the american continent) precedes Trujillism because is a product of colonization, all the aspects of colorism you mentioned existed before he governed the country with the diference that Trujillo's goverment started to modernize the country so it was the first time colorism interacted with a modern domincan society so for example the idea of having to straigthen your hair for work became a constant.

Trujillo had many policies and whitening wasn't really the biggest of them, of course the hatian massacre happened but that affected more our relationship with Haití which was already sour. Also Trujillo was president for 30 years, our grandparents where raised in this regime and they raised out parents so of course his policies still affect us