Why did the Aztecs live in Lake Texcoco?

They were looking for a safe place to hide from their enemies. They were weak, despised and abused by everyone. Eventually they would become strong and turn the worthless swamp island into the heart of cruel and powerful empire. To stay safe they used causeways. Causeways were used to keep enemies from bothering them. The causeways were made of boards so that they could be easily removed.