Forms of peanut butter were already popular before Rosefield's innovation. The problem was that the oil separated from the peanut grit and did not keep. Rosefield's patented homogenization solution was to partially hydrogenate the peanut oil to make it more miscible with the peanuts.
The existing peanut butter had a flaw: the oil separated from the peanut meal, making it unusable.  Rosefield's solution involved a process to make the oil more compatible with the peanuts by partially hydrogenating it.