If runaway stab trim caused by MCAS is indeed what's happened it might not have been obvious enough.

It could well be that it is obvious for anyone with the proper training, but then maybe not all airline pilots get the proper training? Or if they have the training but are pushed to hard in the name of cutting costs, and profits?

However, if it indeed was expected to be obvious to all pilots, why even - as I understand it - have the warning on the optional HUD?

Seems like bad safety engineering to have extraneous warnings possibly increasing cognitive load in a a crisis situation.