Soft and brittle wood from growing so fast. Plus, all main branches come out from a central point (whorl) about 3-4ft up the trunk. That's the weak point and where they break-off.
The other cultivars - Cleveland Select, Aristocrat, Redspire etc - last 30-40yrs, because the lateral branches are spread evenly up the main trunk, and taking pressure off that break-point on the Bradford.
same thing happens to old folk.....down yonder
Bradfords suk.