Brain teaser-What makes differential seals blow when differential bearings start to go?

99 Honda Accord, 4 cyl. BAXA Trans.
It is well known that when the differential bearings start to go, the differential seals at the output shafts also start to leak and or blow out all together.


What is the reason the differential seals at the output shafts leak and or blow when differential bearings start to go? Turbulence? Heat?? I do not know the answer to this question but not knowing has got my curiosity up!
Does anyone know answer??


Thanks in advance!