Poor maintenance. Pilot skills in hand flying and unusual flying and recovery so different (overseas they don't always come through a normal US style GA background).
If they would have looked more closely at the US, they would have found that this system was triggered (and resolved) I suspect pretty frequently by US pilots - ie, the pilots in the loop compensated for the design weaknesses which was the boeing thinking historically. US pilots have played that role on many planes, usually mfg then fixes the issues as well.
If they are going to continue to sell internationally in the markets they want to they actually need to think about doing more automation and flight protection stuff - more computers - not less.
This may never have been the major issue it became if they had focused on a major carrier like Southwest (very experienced crews).
The whole MCAS thing was garbage, interesting they are pinning it on this guy. He does say internally he lied to FAA (unknowingly) as they weren't fully familiar with MCAS modes and edge
Edit: Appears I was wrong - good maintenance in US seems to have been key saving thing.
"Following the recent events in Indonesia and Ethiopia, U.S. flight data was analyzed to understand whether indicators may have existed that could have been addressed, and potentially preempted the accidents. The data showed zero incidents of runaway trim on Boeing 737 MAX 8 aircraft in the U.S. system,” says the report from the special committee.
Good job A&P folks!