Do you think Sony and Bamco / FROM have some kind of handshake deal that allowed Dark Souls to be a so similar to Demons Souls?
Obviously devs make similar games and spiritual successors all the time but Dark Souls literally reuses assents and sound effects left and right.
Demons Souls to Dark Souls is like what if Destiny had a bunch of Halo guns and sound ques and characters in it.
Maybe Sony dropping Demons Souls reverted some rights back to FROM.
Oh and dropping Demons Souls has to be one of the bigger missteps a publisher has made. Then again Dark Souls having the wider audience kind of made it the success it was... I dunno.
You're really over estimating the money brought in by the Souls games, and ignoring the fact that Sony got an exclusive game from the Souls developer a few years later. It's nowhere close to missteps like uDraw.