The sleaziness of Donald Trump is obvious to anyone who bothers to look. He recognizes no limits to his personal conduct, as he recognizes no law that might restrict it.
Among the creepier aspects is that Trump thought saying a would be sex partner reminded him of his daughter would be seductive.
The story of Stormy may not be legally required. But it's essential to better understand Trump's behavior. The jury needs to understand why he would break the law to hide it.