Originally Posted by
Sailvi767
I am having a hard time understanding why
Unless you're doing it every day, the moment you get upside down, your brain tends to turn into mush and just do what is instinctive. I.e., apply the (what is normally the) "oh **** make the airplane go up" control, i.e., aft elevator, regardless of which way was was actually up. Note also, how he said "easy roll to the horizon" which was to the left, but went right instead.
All this on top of the fact that it was trimmed for +1 G at near stall speed, which will naturally give a few positive G's past the barber pole.