Rear shock upper mount broke by itself

Hi,

Yesterday, as I was driving out of my garage I heard a thumping noise coming from behind. Turns out the rear shock upper mount broke.

https://drive.google.com/file/d/0B6gWE3O0itxEMUprYm5JTjJ0VVk/view?usp=sharing

How could this happen? I have not driven the jeep offroad for a few years.
Does anybody sell those separately, without a shock?

I've had that happen twice. Probably due to incorrect length either causing the shock to be a bumpstop or limit strap. And those can be bought separately

Stuff doesnt last forever. Hardly broken 'On its own', Its bolted to a moving vehicle suspension, not a shelf in a closet. Look along where it cracked for corrosion/grime, signs that the crack had been developing over time.

Im positive you can find replacements, but there are all kinds of differant sizes/spacing on those, so you will have to look carefully.