I assume by all the exclamation points that you disagree with my opinion on this.... :-) I understand completely, and you may be right of course.
When the axle (front or rear) on a motorcycle is tightened, there are dozens or hundreds of tons of force applied to the axle, effectively stretching it and binding all the inner tubes together to make a cohesive unit. The inner parts are the bearing inside races, the tubes spacing the bearings apart, the brake support bracket, the hub and the swingarm mounting points. Once that assembly is under tension / compression, it is extremely rigid and strong, and that one of two standard methods used to make a bearing mounted assembly (the other being to do a similar thing with the outer races and associated mounting parts). Under that kind of stress, when a bearing fails the device that is rotating on the bearing(s) must either seize and stop immediately or cause something else to break free and rotate; as it is not likely that the rear wheel assembly of a motorcycle (at least a large motorcycle, perhaps a scooter could do it) can stop virtually instantly, something else must become a pivot point. The weak link in the assembly is usually the press fit between the outer race of the seized bearing and whatever it is mounted to (the wheel in our case). The force holding that race in place is much, much less than the force binding the axle together. The next failure point after that, assuming the outer bearing race does not break away and spin, is the axle itself which would most likely simply break.
What appears to have happened on your bike is that the right side axle bearing failed (most likely due to contamination and corrosion due to the seal failing), seized and the axle rotated inside the right hand swingarm. As someone else said, perhaps there was a burr or some type of obstruction on the axle when it was assembled and that caused the axle nut to tighten without actually bringing much, if any, tension to the axle itself. Whatever the underlying reason, I believe that failure is not possible given the materials used and the force produced on a tightened axle.
Funny coincidence but the seal on the right hand side of my C-14's rear axle has failed and needs to be replaced. I have the new one but have not yet yanked the rear wheel off the bike to replace it. I will take a photo or two of mine while it is apart so what everyone can see what a seal failure looks like because they really do not look obviously bad.
Of course that is only my opinion and I do not think there is really any way to know what happened in your particular case. And again, no offense meant but I can understand why you would be upset with my previous post. At any rate, glad to see that you did not go down when the mishap did occur and that the bike could be repaired within reasonable cost.
And by the way- nice job cutting the axle out of that bike with the saw / drill / chiseling. It takes a fair amount of skill to wield rough tools like those used in such tight quarters without nicking (or outright crushing) something other than what you were trying to remove.
Brian
Conoscete voi come è fatto l'insieme ruota per girare credo proprio di no , asse ,copri asse,cuscinetti,dado!!!, Smontate da voi il C 14 !!!,vi mostrerò con video clip l'insieme
Vi siete chiesti !...un solo C14 in 5 anni di vita in quelle condizioni
Dado non stretto bene !!! ho percorso 14.000 km da l'ultimo cambio treno gomme.
Con dado non stretto non avrei avuto tutto quel disastro,ripeto la causa sta per come è
l'insieme ruota,pernio,copri pernio,cuscinetti.