Why does grape juice ferment faster than molasses even though molasses contains more sugar

Maybe the amount of yeast in juice is higher than the amount in molasses?

Molasses has sucrose as the main sugar (it's unrefined sugar), while grape juice is rich in glucose. As such, the sugar in grape juice is ready to ferment, while the sucrose in molasses has to be broken into glucose and fructose--an extra step than not all yeast are good at.