What were the views of the christian japanese about Lord Buddha and the Shinto Gods? Why they converted when they already had the teachings of Lord Buddha and other great men?

I ask this because I always were interested in the history of feudal Japan and now with the Shogun show and the character of Lady Mariko, based on Hosokawa Gracia, I want to understand what they were thinking in those conflict times.

Thanks for any information.

by MomusVult