Strength training can help reduce injuries from crashes up to a point.

Experience helps too but that’s harder to get safely!

For collarbones specifically? Nothing I'm aware of. At least if the explanation that was given to me for the high prevalence of collarbone injuries is correct, that makes sense. Someone explained it to me as "when you start to fall, you instinctive tend to reach our towards the ground to try to break your fall. So your hand is the first thing that hits the ground, and all the energy of the fall goes up your arm and into your shoulder / upper chest area. And the collarbone just happens to be the "weak link" there and so tends to break."

Now maybe that's just folk wisdom that isn't really true, but it sounds plausible to me. And if we reason by analogy a little, it's not too far off what my surgeon told me when I tore my rotator cuff. I fell and came down on my elbow, and he explained that the energy from the fall pushed my humerus up into my shoulder, and pinched my rotator cuff between two bone heads, which is what caused the tear.

So yeah, not much padding can do about stuff like that I guess.