It was improperly packed.
- Dunnage always should be added to keep contents from moving around.
- As others have said, a flimsy box is substandard, and gear is best shipped in the original box.
- Lacking the original box, or if the original is old, double-boxing is a good option. Often, I use an extra-heavy corrugated box for the outer box.
FedEx in my experience has a better reputation than UPS, but I haven’t found that borne out in less actual damage. Anything should be packed to withstand a short fall.
You could ask the seller to pay for the damage if you took photos of the box, the packing, etc. You could even escalate to a PayPal dispute if in fact the packing was substandard, and that caused the damage. Any kind of dispute will be more difficult if you don't have photos.