Answer:
The main reason they left was because of the draught. There are also theories about Marauding enemies and scientists suggest that poor sanitation and environmental degradation also caused them to leave. also it was difficult for them to grow corn.
Step-by-step explanation:
The South where they migrated had more rain that they could rely on
( I hope this helps! I couldn't find very much information except for this because most of their migration is Mystery. have a wonderful day! And if there is anything specific that you need for this answer please comment below in the answer!)
:)