Chains are pretty much a commodity item, and the OEM chains used by manufacturers are the same as ones sold at
retail, although the price they pay is a small fraction of what the retail is when you buy it bulk by the mile.
The likelihood your chain was "worn out" is small, but your mileage may be more than you think. Probably not the
3000 miles or so a reasonably cared for chain should last. That is what I get anyway, like dabac. Be aware that (some)
new chains have a functionally nice lube on them but it is very sticky and a dirt magnet. Consider at least a heavy
external wipedown with a solvent (mineral spirits) soaked cloth to remove as much of this as possible.