This article about margarine doesn’t say that, and contradicts that. I’ve seen videos that agree it was originally made for humans.
After the French Emperor Napoleon III issued a challenge to create a butter-substitute from beef tallow for the armed forces and lower classes, Hippolyte Mège-Mouriès invented margarine in 1869.
Margarine was synthesized as cattle food but deemed too unhealthy for them to eat.
This article about margarine doesn’t say that, and contradicts that. I’ve seen videos that agree it was originally made for humans.