There is a very high overlap in kids who have ADHD and ODD. Children who have ADHD are prone to be distractible and impulsive, which often sets them on a collision course with behavior expectations. Repeated patterns of negative interactions with parents and other authority figures can lead to developing ODD.
Children who had a lot of difficulty soothing themselves as toddlers and continue to struggle to manage emotions like frustration and disappointment as they mature may be at risk of developing ODD.
Experiencing life stress and trauma can also be a risk factor for developing ODD.