I tried this on Xplane 10 a few times. Unfortunately, the closest model I have is the much newer F-4. I find that even with the F-4 running at near stall speed and then going into the climb if the loop is too small the plane stalls in the vertical ascent which one wing may lose lift first. It's hard to tell if the video point is actually a stable horizon image. If it is it does appear one wing loses lift and then the plane teeters a bit.
Either way once the stall happens you can't recover because you aren't high enough to trade altitude for speed.
Steps
1) Fly at 130 knots with full flaps.
2) Throttle pull in the flaps and go into the vertical climb of the loop.
3) I find that an aggressive tight loop is around 2250-2500 ft / ~750 meters peak. If I try to do it tighter and only go to 2000 ft the plane stalls in the ascent and although look likes it's still under control it has not enough airspeed or altitude to ever recover lift.
Also I did this completely on instruments. If I try to do it without I crash every time because I have to idea where I am. Even then it's hard because when the horizon disappears it's like being blind. I guess if you do this all the time you kinda know where you are or should be. But I normally try to fly with a horizon
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From the original video it looks as though he is trying to trade altitude for speed as the descent seems to appear controlled and straight down in order to recover speed and regain lift later but it never happened and he was trying to find the clearest place possible to put it down. But without lift you can't control the plane. To me this looks like what has happened because the plane has not much lift at all near the crash point as it appears to be descending 20 feet or more per second.