He wanted to find a shorter route to India, not necessarily avoid going through the Middle East.

Portugal was a powerful nation at the time, with their empire spreading across the Middle East, this was trouble for Spain who wanted to trade in India. The territories controlled by Portugal made the journey very long and awkward for the Spanish Empire.

Christopher, who was Italian contrary to popular belief, thought the world was smaller than it actually is (he didn't think the world was flat. At all.) so embarked on a journey to find India travelling the other way around the world.

When we found what we call the The Caribbean, he thought it was India and that's why it receives the name The West Indies.

But yeah, Portugal and Empires made it difficult for the Spanish to trade.