It is indeed difficult to envisage what other situation they could imagine involving a 15º nose-up attitude / low indicated IAS / TOGA thrust / massive rate of descent that they could have believed to be the case, rather than coming to the conclusion that the aircraft was stalled.
Given how many times the aircraft announced "Stall" "Stall" (even if it had now fallen silent. . . useful that ; NOT) I am at a loss to fathom why nobody could at least figure out (and announce) that they had stalled.
There is no other upset that would display the same symptoms, at that moment they had lost Situational Awareness, completely & utterly.