Honestly cannot imagine how your collision with a deer could damage the wheel bearings. The wheel itself would need to impact something solid, and it does not look like the wheel was struck at all. Bearings are quite tough, as one might expect.
Top cause of a life this short would certainly be setting them to tight.
Any evidence in unusual tire wear? Bearings that are set to tight usually cause cupping.
I suppose they could have run dry on grease, but it is tough to screw that part up.
Damage or contamination during install is another possibility. Nicks, grit, and such.
Also, one would expect some warning in the form of a growling or moaning noise prior to the catastrophic failure.
1986 300E 5-Speed 240k mi.