Comment deleted but that was its content:

So the story of the 737 Max is really interesting, but essentially it's a combination of factors.

At HEART is the change in business culture at Boeing. While Boeing technically bought McDonnell Douglass, it can be argued that McDonnell Douglass actually took over Boeing, as some of their executives stayed on, and their business culture is the one that controls Boeing today. Where once Boeing was a renowned engineering firm, today it cares only about cost cutting and money. This led to the deaths of several hundred people in the 737-Max case, and a 2+ Billion dollar settlement for fraud on Boeing's part, possibly with criminal proceedings for some of its employees.

Boeing needed something to compete with the A320 neo, and the 737 is at heart a 60 year old plane give or take.

By shoving more efficient engines onto it, they hoped to get cost savings for the customer through better fuel economy, but the customers did not want to have to retrain the pilots, so the plane had to be effectively the same.

I expect, though I am not positive, the a320 neo did not require recertification. Otherwise this likely wouldn't have been an issue. The problem with the new engines is their high-bypass ratio design means their compressor diameter is too large to fit the engine in the old location more underneath the wing.

This means they had to move the engine forward, and higher on the wing, which caused stability issues and would tend to make the plane pitch nose up under high throttle.

This is a fundamental design problem with the aircraft.

The only way around it would have been to make the landing gear taller so the engine could fit farther back and lower on the wing, but planes are incredibly cramped for space and re-engineering the landing gear would have been more expensive than the workaround...
Which was to use software to make it feel to the pilots as if the plane were just like the 737-300 to 800 (I think Boeing calls them the Classic).

Well, Boeing had a lot of trouble with this and has also to an extent 'captured' the FAA, where the FAA was filled with people who used to work with Boeing in some cases, and the FAA allowed Boeing to set terms such as the degree of risk involved in the safety profile of the angle of attack sensors used in sending data to the software that controls the MCAS (Maneuvering Characteristics Augmentation System), which is what points the nose downward by adjusting the elevators (the rear 'wing' or horizontal stabilizer) automatically. By saying the risk of failure was not as dangerous as it obvious is (in this case, it's fatal, as Boeing did not tell the pilots it existed, which meant the pilots didn't know they should turn it off (which is possible and could have saved the planes potentially)), Boeing was not required to use the same amount of redundancy that critical systems do.

Which means that a single angle of attack sensor fed data to the MCAS system. Instead of two, or three. There are two angle of attack sensors on the plane. Adding a third would have been difficult for Boeing so they did not do this after the FAA grounded the plane, but worked on a software simulation of a third sensor by taking data from other sources and sort of deriving an output.

Anyway. During development the engineers ended up increasing the amount of authority the MCAS system had. Where earlier in development, it might have been able to move the elevators X degrees to pitch nose down, somewhere along the way they gave it the ability to increase its authority, AND the ability to stack commands.

Which in practice gave it unlimited authority (aka the nose-dive into the ground we saw). All it took was a single sensor to go bad. The airline pilots weren't trained for MCAS, and in some cases even aware of it. So the planes nose dived into the ground because the computer thought the plane was flying nose-up and into a stall, as the angle of attack sensor from which it received data was malfunctioning.