My guess is the weld has made the steel brittle - you can see the crack at both welds. The bracket has probably cracked due to the rail flexing as a result of the cracking.
Of the dozens and dozens of these I've pulled apart or fiddled with over the years the only ones I've ever found not cracked have been vehicles with their original front springs and original size or at least original profile front tyres. Every other one I've had has been cracked and has had aftermarket lowered springs fitted at some stage. Gas shocks make them very harsh too, I've always gone for oil shocks as they don't seem to be as tough on the car.