Were there giants in the ancient world? Did fallen angels procreate with human women, and if so, does the Bible explain how that happened?
Some claim that this was impossible, but the Bible gives us clear and precise details of how the angels sinned with human women and created giants on the earth, both before and after the flood of Noah’s day. 
Why did God destroy everything that had breath in the global flood, and then later, give Joshua the same command regarding specific tribes in Canaan? These are very important questions.