Landslide be more likely on a steep mountain

Why would a landslide be more likely on a steep mountain than on a gently sloping hill?

The steeper the slope, the easier it is for objects to slide due to the force of gravity on them.

Imagine a marble on a completely level surface, it doesn't roll anywhere because gravity is pulling down on it and it is perfectly perpendicular to the surface, but once you start creating a slope with that surface, the angles change causing the marble to roll, the steeper the angle, the easier it is for objects to slide, fall, etc.