Answer:
Because he tricked them and gave them useless glass beads and they gave him nice stuff and the best they had so when they found out they were hurt by it.
Step-by-step explanation:
I mean think about it,what if someone gave you a clear quartz and said it was a diamond and you gave them you new phone or new computer because in your mind you were thinking you could get some way better stuff if you had a diamond.
Hope this helped you.