I keep a section of 2×10, about 18" long, in the van to set the jack on should we ever have to change a tire. Besides stability, It helps to give the jack that 1-1/2" head start.i can't say for sure as it fell right before I got there. But all signs point to uneven surface. The ground was level enough, but the asphalt badly broken and heaved in places where the car was. My best guess is that the jack wasn't sitting flat and it fell out away from the vehicle, judging by the way the jack was bent at the top (which happened because of the fall, not the cause of it). Definitely not a jack failure.
It's possible the jack was put a little too far to the rear, the correct point is far up front on the pinch weld indicated by two cutouts, most people just pick a random spot that looks "good enough", which would likely be back too far on this vehicle.
Over a two or three year period, 2014 - c. 2016, my wife called me at work three times with flats.
Once she hit a bad pothole and blew both a rear tire and the shock, and twice she hit the curb and damaged the sidewall. No problem getting her going again.
No problems since then - it was just a bad run where we had a lot of stressful stuff going on, and she was probably distracted.
Her dad was long past doing that sort of thing by then, but I think she always would have called me first, even 25 years before that.