Flight simulators cannot replicate the somatographic effect, but instead, they rely on tilt angles to fool occupants into thinking they are manoeuvring such as accelerating down a runway while remaining firmly bolted to the floor.
Just think about this for a moment. They already did a go-around. They did second approach fully expecting to go-around again. The second go-around was completely and utterly normal until they are at clean speed and in a config that one can assume is flaps up. How in God's name can both pilots in a low authority gradient flight deck suddenly become so disorientated to the extent that they go from a climb to -15,000fpm in 5 seconds with no evidence of any attempt to recover (the opposite in fact)? It just makes no sense whatsoever.
Something else happened.