What was the main reason why one tribal group was so incredibly cruel to the other?

Question

What was the main reason why one tribal group was so incredibly cruel to the other?

Answer 1

If we analyse facts deeply, it's not a tribal issue but rather a social and political manner. A certain tribe might be toiling all year round and eventually enjoy the fruits of their labour. On the other hand, the other tribe might neither be as organized nor as successful as the other. This will naturally create tribal tension and and with a bit of political catalyst it will eventually spark into something worse.