I'm not terribly surprised.
The Sengoku, as awesome as it is, is a very niche setting for most of the TW fanbase. A lot of people claim RTW as their jumping on point. It was the first game in the new 3D style, and it also got quite a bit of exposure being used for TV shows like Time Commanders and Decisive Battles.
It also helps that there's a number of things about rome 2 that look really fun.
Bookmarks