It's not quite simple, please don't dismiss it as "simple physics". A Simple Physics explanation would be that the diffs fail at different forms of stress. In this case, the rate at which the wheels spin is not one of them, nor are they the main culprits behind it.
The car is equipped with torque vectoring, which sends more or less power to different wheels in different situations in order to optimize cornering and handling. Even if you lock the center diff, which implies a 50/50 power distribution and forces all wheels to have the same rotational speed, you will still have different speeds if your road conditions are constantly varying.
Whatever type of stress the worn, smaller diameter, different, etc. specific tire or tires it puts on the diffs is what will cause it to fail. What that specific type of stress is I have not a clue.
But if I were given the type and amount of stress put on these mechanical components as well as the dimensions of all the components associated with the failure, along with the location of the stress and failure; I will be able to demonstrate a diagram depicting exactly how the failure was caused and calculate at what specific load the stress reached when it caused whatever component to fail.
Will this be easy? Heck no. This is Fundamental physics or engineering (statics, strength of materials, mechanics, general physics, calculus, thermodynamics if temperature and heat was involved said the failure(s), etc.) Will this be even possible? Yes, if one was able to accurately gather all of that data. Is that impossible? Yes, if one did not purposely perform said stresses in a closed, data-gathering-able environment.
Is that impossible? Probably not, but you will never be able to properly collect that data on just a regular day this occurred, taking into account all live and dead loads that were present when it occurred. This is the only reason it will be impossible to know EXACTLY how and why it failed. But you can get the gist of it performing tests in a closed environment while mimicking all the conditions that might have been present at the time.
But yea, it's really far from simple. The concept and theory is simple to talk about. But properly determining what actually happened is as much far from easy or simple as the actual physics behind this really is.
Forced induction can be explained in a sentence is what I'm getting at. Is it simple physics? No, absolutely no physics-related concepts will be as simple as just being able to read about it.
This isn't a shot at you at all, I've just read that on here (these forums not just this thread) way too many times. Sorry about the educated rant, it just really makes me cring when I read something much more complex than what it seems to be, being labeled as "simple physics". Tell the engineers who spent however many years designing the current system that, and I will guarantee you they will feel insulted.
