This is a documentary not a mystery film, so I won't call this review a spoiler.
Why he did it was partially answered, but not discussed was that we all want to be known for being successful. Fortier realized that with his sperm mixed in the chance of success increased.
As he became known for being successful (with lots of profit to boot) he kept doing what worked... mixing sperm specimens.
As mentioned, DNA testing was nonexistent at that time so he knew he'd be remembered for what he was: a VERY successful fertilization doctor.
Why he did it was partially answered, but not discussed was that we all want to be known for being successful. Fortier realized that with his sperm mixed in the chance of success increased.
As he became known for being successful (with lots of profit to boot) he kept doing what worked... mixing sperm specimens.
As mentioned, DNA testing was nonexistent at that time so he knew he'd be remembered for what he was: a VERY successful fertilization doctor.