I think Richter knew about Olrox inhibiting the castle but did nothing about it because there was no need. Richter was made the lord of castlevania until Dracula's ressurection was finalized. In tearms of what Olrox thought about this I can only think of two things.
1: Richter was made the lord of castlevania by Shaft and being under control, posed no immediate threat.
2: If Olrox wanted to off Richter he wouldn't stand a chance. Richter is the most powerful vampire hunter ever to walk the earth and he was able to bring down Dracula. Olrox is no-where near as powerful as Dracula let alone Alucard and with this knowledge in mind he would not push his luck. And since Richter was made lord of castlevania Olrox would be expected to obey him to some extent. That my analogy of the situation.
-X
i totally agree here...and in LoI Dracula "needed" the soul of a powerfull vampire...maybe Olrox was a "replacement" if it was needed. or just to make the castle's defense stronger...like giving part of it to him and some to Galamoth...although i guess both of them had in mind to one day defeat Drac and conquer the crinsom stone, or the castle itself...