I asked my Mom if it was a groundbreaking thing to have a person of color be a lead on TV. She said the 'Latin lover' was a big thing in the 50's. Was that true? Was there one cultural icon that lead to this phenomenon?
Hi, there was a question on Desi Arnaz just recently. It won't answer all of your questions, but may be interesting as a start.
As for the origin of the "Latin Lover" trope, if none of the film historians jump in here, consider x-posting to a sub specializing in silent films.