Pulp could not resist the lure of the crazed doctor or scientist legend. As well, in the early 1930's, the pulps went a bit nuts with their fascination for dungeons and red robed maniacs who tormented their captives, a pulp seraglio, if you will. These works are often referred to as 'terror pulps'.
Some are so tasteless that I discard them, but most are at least amusing.