Automatics can stall rolling back significantly in forward gear. I've had it happen a few times in various cars. I don't think anything is particularly wrong with your car, at least not based on this happening.
It's just what happens when you put a load on the engine that it can't sustain without stalling. You have to remember that being at a stop in drive, is not the same thing as being at a stop in 1st with the clutch pedal engaged. Your car is still in gear and it is still trying to go foward and transfer the load from the engine to the transmission. You would actually have less load on the engine in neutral.
So now when you're on a big hill, the load your engine is sending through your torque converter can't overcome the hill's gradient, the car rolls backwards, turning your wheels the wrong way and putting even more load on the engine via the transmission and torque converter than you would at a stop. So the engine stalls from that load, just like it would if you didn't have enough revs/momentum in a manual to sustain the load created by dumping the clutch. You could even out-brake your torque converter and stall an automatic in some circumstances. That's similar to spinning out or braking too fast in a manual and being unable to hit the clutch fast enough to keep the engine from stalling, similar idea but with the TC lock/unlock.
Engines in automatics can stall just like any other combustion engine, so there's not very much mystery. However I can see how it's super counter intuitive, since most automatic drivers never experience a stall, so the first thought is "OMG I broke the car". In reality once you break it down to the mechanics at play you can see why it's possible to stall an automatic.
Same thing happened to me but I was mudding haha. I got stuck and was not flooring it but giving it gas and once I released off the gas pedal the truck turned itself off.
Similar to the out-braking scenario. Your TC was locked up as you were spinning your tires and then you let off the gas and they rapidly slowed down before the TC could unlock. Load back to the engine and it stalled.
, but back to this...YEAH i just simply put it in park while it was off, and switched the key back to ACC , then turned her on....really weird.
