Sorry for the slow response as I have been on the road. What you have provided here is very little data, however we can speculate a bit from it: the OB bearing suffered a catastrophic failure. It is black, the discoloration most likely from thermal energy. It is also likely that this heat was the result of friction. This friction could have resulted from a breakdown in the lubrication barrier of the oil. If this occured, it may have been caused by the ingression of a contaminant, such as the cleaning agent you mentioned. This contaminant could have reduced the viscosity of the oil. Viscosity is the main property of the lubricant which maintains the separation of the rotating and static surfaces. If reduced, contact, friction, and heat could have been the result. I understand that this is the direction that you are leaning, however, as you can see from my previous statements, there are a LOT of "ifs". What you are really wanting to accomplish here is Root Cause Bearing Failure Analysis. This requires that a highly disciplined process be adhered to which assumes NOTHING. Assuming is an easy trap to fall into, but must be avoided at all cost in order to arrive at the most likely and objective conclusion. SKF is one provider of this training (one that I would recommend) and I'm sure there are many others as well. If you are really serious about finding the root cause of this as well as future failures, I would highly recommend that you seek formal training in this field, or consider hiring a consultant.