How did the 737 MAX get gounded, perhaps for ever?

It goes back to 2010 when Airbus announced a re engined A320, their workhorse single aisle air liner, that would save 15% on fuel.  Next year 2011, American Airlines told Boeing they better have a reengined 737 or else American would buy the Airbus 320 neo.  Boeing started the 737 MAX project a year later.  This project was a straight forward engine swap, replace the existing engines with newly designed engines that would give better fuel economy, leave the rest of the 737 alone.  It took Boeing four years, until 2016, to get the engine swap designed and built and get the first flight accomplished.  This is a rediculous length of time.  Back in the day, the British were able to swap out an anemic US engine for the 2000 hp Merlin engine on a North American fighter plane over a weekend.  The result of the British engine swap was the famous Mustang fighter.  You would think if the Brits could do it in a weekend, Boeing ought to be able to do the same thing in less than four years. 
   One of the constraints, was the 737 MAX had to fly like the preceding 737s.  And, the bigger engines of the MAX had a tendency to push the nose up when power was added.  So Boeing added code into the autopilot software to push the nose back down and make the new MAX fly just like the old 737.  Unfortunately for Boeing, the new code, the Maneuvering Characteristics Augmentation System, MCAS for short,  could fail disastrously.  When things went wrong, MCAS could dive the plane into the ground.  This happened twice within a few months.  All on board were killed in both accidents.  Which caused the 737 MAX to be grounded.  It's been grounded for 5 months now. 
   Boeing hopes to present corrected autopilot MCAS code to the FAA for approval this month, September.  FAA, being a government bureau, can take as much time as they like to decide to OK the new code, or call for yet changes and/or testing.  When (and if) FAA ungrounds the 737 MAX then all the other regulators around the world will begin to unground the plane for their airlines and airspace.  At this point Boeing is hoping to get the 737 back in the air before the end of 2019.  This may be a vain hope.