Sandra Bullock and Jesse James's divorce was primarily attributed to infidelity, as James was involved in multiple extramarital affairs. This betrayal undermined the trust in their marriage, leading to significant emotional distress for Bullock. Despite their initial bond, the revelation of his infidelity ultimately made it impossible for the couple to reconcile, prompting Bullock to file for divorce. Infidelity often creates irreparable damage in relationships, and in this case, it was the decisive factor that ended their marriage.