YMMV / Stranger Things S 3 E 6 Chapter Six E Pluribus Unum

• Genius Bonus: Despite laws in California being ruled no-fault regarding divorce in the 1970s (when Billy was a child), a judge can decide what they think are the best interests of the child of an adulterous marriage. Likely either Billy's mother couldn't prove Domestic Abuse or a judge sympathized more with his father.
  • Or, given the tenuous status of women's rights in the 1970's in regards to employment and discrimination, it could just be that Billy's mother could not find a job after her divorce and could not support him, leaving his father as the logical choice for custody.