I don't see any nose down attempt to recover from the apparent stall. It takes some willpower to stuff the nose down at 300', but I'm still here to tell you it just worked for me - in a glider.
There's a moment of surprise, WTF is this?!, and incredulity when it goes pear shaped. Keeping the stick back won't work.
In my case I was caught by a vortex / downburst downwind of terrain, but it looks pretty flat in this case.