The biggest things are the relationships of the CG of the airplane to the ground and wheel contact. At slow speeds aero forces and moments don't get into it much.

Assume for a moment that the wheels don't turn and that they are directly below the CG. The moment causing the nose over is the weight at the CG times the height above the ground. That moment must accelerate the fuselage moment of inertia about the wheel contact point with the ground.

The forward position of wheel and ground contact point relative to the CG also changes the answer. It adds a anti-noseover moment equal to the weight at the CG times the longitudinal distance between the CG and the wheel contact point. So it tends to counter the moment in the second paragraph.

The wheels free to roll makes the overturning less strong and it also depends on the diameter of the wheels. Big wheels make it less likely to nose over. Free turning wheels make it less likely to nose over.

A larger moment of inertia of the fuselage will make it less prone to nose over. That you can get with longer fuselage.

My GWS is a beauty to land. Its landing gear is relatively short, the fuselage is not too tall, wheels are big (not compared to a big grass blade though) and the tail is long. It is a good example of a bipe that is easy to land, expecially on concrete.

The Camel has a taller landing gear, tall fuselage and and a fairly short fuselage which makes it so much easier to nose over.

How to stop it.

1. Land in short grass and hold in lots of up elevator while the aero forces are still in effect.

2. Get a better pilot. (sorry that just snuck out, couldn't help it)

Does the springness of the landing gear effect the nose over. Only if it stops the wheels from rolling or causes them to toe out to increase their drag on the ground.