So far nobody asked Boeing how something so obvious and big could slip thru their safety process including document reviews, walk-thru, inspections, accessments and linked documents on several layers of detail.
Boeing must have known something was up if the computer modelling showed that MCAS needed to provide 0.6 degrees correction, and in flight testing, 2.5 degrees was required. That is a big disconnect between design assumptions and actual.
What went wrong within the engineering process and how can you prove that no other hazards excaped thru the exact same hole in your process.
There are 4 interfaces for the Horizontal Stabilizer portion of the Flight Control System (FCS), which link the autopilot trim, electric trim, manual trim, and MCAS trim to the stabilizer trim system.
EDIT: Just read this...
Boeing is currently examining whether or not the current MCAS interface between the MCAS computers and the horizontal stabilizer trim motors and Horizontal Stabilizer Jackscrew is compatible with the MCAS software updates.
As MCAS was an option for other 737 variants, (as well as other Boeing aircraft) it would be interesting to see what those systems provided as a correction. (perhaps to the 738?)
On a historical note, it appears that MCAS has been considered for most Boeing aircraft, but that the vortex tabs solved the problem....now we know why they are still on all of the wings.