Why did mr . Hiram b Otis buy canterville chase knowing tht it was haunted ? 

Mr. Otis wasanother practical, inflexible and pragmatic  American with a modern outlook. He initially didnt believe in ghost and he felt that even if it existed in the chase he would buy him too along with the mansion.this just conveys how logical and pragmatic american nature is. Being modern he just poked fun at the traditional beliefs of the british culture and aristocracy.