Medical Sciences SE and Law.SE were launched roughly at the same time, in March 2015 and May 2015 respectively. At the time of the launch, I thought the two sites would be equally successful, as Medical Sciences and Law occupy a key role in our lives. I also considered Medical Sciences SE and Law.SE as being very similar in the sense that both may require expertise and attract possibly referenced answers. They even share a similar disclaimer ("this site is not a substitute for individualized advice from a qualified legal practitioner" and "Medical Sciences Stack Exchange is not a substitute for medical advice, individualized diagnosis or treatment by a healthcare provider.").
However, 8 years after their launch, Medical Sciences SE has been much less successful than Law.SE. E.g., it has received 4 times fewer questions. Here are more stats:
Why has Medical Sciences SE being much less successful than Law.SE?