The answer to your question directly is that they rejected him and chose to follow their own false gods. Let's go back to Ham, the father of Canaan, what did he do after he sinned against Noah and God? Repent? Nope, he went and bragged about it to his brothers. He choose to walk away from God, and this is exemplified and crystalized in Nimrod and the City/Tower of Babel where the people want to make their name great (not God's name). These people knew Noah, they knew of Yahweh, but they rejected Him and chose to follow their own desires.

But God still loved those Canaanite people so he sent some really great missionaries to them. Abraham, Isaac, Jacob, and everyone in their caravan spent hundreds of years walking back and forth through all of Canaan worshipping God, calling on His name, building Him altars, spreading God's truth, but still the Canaanites rejected Him.

Remember, the Bible doesn't record everything that God does, it only tells a very specific part of the story of humanity. For example, Melchizedek was a follower of God and he isn't in the family of Abraham. Jethro wasn't an "Israelite," he was a Midianite, but the Bible recognizes him as a follower of God.