Demon's Souls was indeed first. It was published by Sony in Japan, and they retained the IP rights. From Software created a spiritual successor in Dark Souls for Namco Bandai which let them do a multiplatform game. In terms of gameplay and theme, they are very similar titles, but structurally Demon's Souls used a hub world from which you warped to a number of differently themed environs. Dark Souls used a totally connected open world which connected various distinct regions in ingenious fashion. Dark Souls, of course, sold really well, earning a sequel, but there are many inside Sony Computer Entertainment who remain fans and felt they really missed the boat by failing to bring Demon's Souls outside Japan themselves. Contracting From Software for an exclusive follow up, if not a direct sequel, made a lot of sense.