The reason for development of MAX was purely commercial. Their biggest customer the south west airline wasn't prepared to wait for completely new aircraft and was thinking of buying the AB neo. The 737 with low engines clearance we're not in position to accommodate a larger fan so it appears they juggled with attachment positions which in turn made the aircraft unstable so had to design untried concept of MCAS and installed it through the back door. So far it was fine but now what?
https://www.google.co.in/amp/s/amp.ft.com/content/c9ebe8c4-24d7-11e0-a919-00144feab49a