Why did the Aztecs decide to settle in tenochtitlan?

The Aztecs choose the location because it was believed to be the place where their god had told them to go. The sign they were looking for was a Eagle eating a snake on top of a cactus. The area was a good place originally because it had a very big variety of bird life. The land was also very little and it was not until they expanded it and adapted to the isle that things got better.