Even if the pilots had been fully briefed about MCAS, its potential failure modes and effects.......
How long would it take to work out that you suddenly had runaway stab trim issues? - whilst you were still struggling to stop a nose-dive? actually not "A" nose-dive but repeated nose-dives?
At the altitude reached, how long would the pilots have then had to work out and implement the correct actions to regain control and avoid terrain?