If I only want what others seem to want, then where did all the wanting begin?
Girard addresses this in the chapter in 'Things Hidden' on "Hominization", ie how we transitioned from just another ape into humans. The time we spent as helpless infants increased as we evolved, and so the requirement to closely imitate our mother, family, society, became essential to survival.
The other only needs to "seem to want" the object, not actually want it. But yes, someone must have wanted first, and apparently it turned out to be advantageous.
Since our inception, we all want to be free, we want to be the enjoyer