RE3 was possibly designed around the PS4 first than ported to the X1 with little optimization.
Also a game running more frames is easier to hit than a game hitting max resolution. It takes more power to hit native 4k from 1080p than to go from 30 to 60 frames.
If Capcom wanted, they could have easily reduced the resolution for a better framerate if they wanted a quick fix.
Games like these are lookers, so they opted for 4k because it doesn't really need 60 frames.