I didn't even think of the Maxim connenction. You could definitely tie it in with that. However, I also thought of something else.
So, Dracula brainwashed Soleiyu and turned him into his lackey so he could be revived by Soleiyu's holy powers, right? That makes it possible Soleiyu was also responsible Soleiyu was responsible for the revival of Dracula's castle. Then I suddenly remembered there's actually a game that downright confirms the Belmont family has the power to bring back Dracula's castle! Namely, Curse of Darkness.
Hector gets manipulated into breaking the seal located in the Infinite Corridor and this act results in Dracula's castle coming back. The blood of the Belmonts acts as a key to this place and I believe it's implied Trevor was the one who put that seal there. Which makes we wonder if Soleiyu was actually hanging out in the Infinite Corridor, trying to break the seal, while Christopher was fighting through the four castles.
Also, it would explain how the castle shows up in SotN before Dracula was even revived: Richter was the one who broke the seal which allowed Dracula's castle to return.