Because most of the weight of the ice falling away below. Make the center of gravity of the dolls has ignited is low, so no matter how your approach pushed its gravity center is not out of the base image.
Because the majority of the Rings weight on the bottom. Makes the center of gravity of the Rings is so low that the vertical position of the center of gravity is pushed out of the base image.
Because of the weight of most of the tumbler is below. The center of gravity of the tumbler is low. So, no matter how the position of the center point to push weighted out outside the base as shown below.