I pretty much bend metal for a living. I'd agree with a comment above that it was likely from a large pothole. The force on that angle is from the tire/knuckle trying to go up, and the spring/shock on that lower control arm trying to keep it down and what you found is the weak link. I wouldn't call it weak but when you hit, i'm assuming, the immovable object, thousands of pounds of force was absorbed in that bend. I don't know much about the older billet ones but to bend that angle, would likely also pull the threads out of aluminum. I dont think that it will bend much further or even break, its almost close enough to tensile force not to go anywhere. I'd just get a new angle, maybe one bent from A572 rather than A36 and just keep an eye on it.