Wtf why didn't the butler and his aids tell him? Did they think it wasn't important enough...

Apparently poisonings there is like, getting the mail?

Poisonings for the men also they poison themselves it isn't a third party thing. It means that they have spies/agents in their house. It is important for security even if she weren't the target. Doubly important since good servants would have noticed that the masters give fucks about her safety. So many fucks, like all they fucks they have to give.