the reason FOR our confusions:

After reason, use the preposition for, not of:

✗ The main reason of poverty is unemployment.
✓ The main reason for poverty is unemployment.
✗ A doctor can’t operate if he doesn’t know the reason of the illness.
✓ A doctor can’t operate if he doesn’t know the reason for the illness.

source: macmillandictionaryblog.com/language-tip-of-the-week