Why did dally commit the crime?

Dally committed the crime out of desperation and a desire to protect his friends, particularly Johnny. Feeling the weight of his troubled past and the loss of Johnny, he acted impulsively in a moment of emotional turmoil. Dally's actions reflect his deep sense of loyalty and the hopelessness he felt in the face of their dire circumstances. Ultimately, it was a tragic culmination of his struggles with identity, belonging, and the harsh realities of his environment.