The bit you put between brackets '(intended)' is the key here. What they intended was one thing, what they got was an entirely different thing. The stabilizer being as large as it is and the degree of authority afforded the MCAS system could cause the tail plane to deflect to a degree that the stick could not overcome it at all, the elevators are simply not large enough to counteract a tailplane that is trimmed purposefully the wrong way to the maximum deflection, in part because trimming the tailplane wrong also limits elevator effectiveness.