I find conspiracy theories about the MAX pretty hard to believe. What is easy to believe is a Boeing management engineering culture that prioritized the absolute minimum changes to the 737 so that Boeing could advertise upgrading to the Max would not incur any training cost to airlines. This combined with the fact that the inevitably individual engineers work on one small part of the aircraft perhaps without a full realization of how "their" system could effect others results in the fact that the AOA sensor has now become a single point of failure which can result in so much uncommanded down trim being applied aircraft control is lost.
The big picture question is IMO what and how should regulatory oversight work in a world where aircraft feature increasingly sophisticated materials and complex integrated electronic architectures. Is this accident the canary in the coal mine for all regulators ?