I don't know what was the cause of the accident. What I DO know is the Chineses already know the cause of the accident, for two reasons:
1.I flew 10 years in China until the pandemic came, and, I know that all airplanes in China continually download both CVR and FDR through out the flight and send it to the cloud. They then keep it for 3 month. So, the bulls..t that the "black boxes"are severely damaged is just an excuse to not spread the real causes of this accident.
I had a small incident during the taxi departing for an 8 hour flight. By the time I landed (8 hours afterwards) they already had both fdr and cvr data in hands.
2. IF they had any doubt it was a plane failure , they would never have put the 738 back in service again.