Many Pseudonyms? Probably Alternate Personalities

—Søren Kierkegaard https://en.wikipedia.org/wiki/S%C3%B8ren_Kierkegaard

—Fernando Pessoa https://en.wikipedia.org/wiki/Fernando_Pessoa

—Charles Hamilton (Frank Richards et al) https://en.wikipedia.org/wiki/Charles_Hamilton_(writer)

—Stendhal (Marie-Henri Beyle) https://en.wikipedia.org/wiki/Stendhal

Indeed, any time writers use one or more pseudonyms, even if they claim it is only for marketing purposes, be skeptical.