You know, I like to think there's a bit of backstory so that Lucius and Severus didn't exactly talk about what Lucius would try to take from Harry. But after hearing Severus' thinly veiled insecurities over the years, Lucius knew.
I'm so glad you thought this was romantically twisted. Because it is. And honestly, I like to read morally ambiguous!Snape, but I don't write him. This was less Severus being a twisted fuck and more him really needing to know Harry loved him. This insecurity just took a different twist than I usually write. Instead of pushing him away, he had him kidnapped.