In what ways was the development of a body cavity or coelom an advantage for bilaterally symmetrical animals

The advantage is that the animals with bilateral symmetry can find food and mates and also avoid predators because they have sensory organs and good muscle control. An example of such animals would be human beings. Additionally, bilaterally symmetric animals have sensory organs focused at the head which interacts with the environment before the rest of the body does, which allows quick reaction and ability to be motile.