This is pretty easy to reason through: if a girl knows nothing about the world, a safe place for her to be is with someone who knows more. If a girl knows how to function in the world on par with a boy/man, or at least has visibility into a future where she can, there is no longer that fear/dependence cycle locked in.
eg How Much Education Is Needed to Delay Women's Age at Marriage and First Pregnancy? https://www.frontiersin.org/journals/public-health/articles/...
The power of education to end child marriage - UNICEF DATA https://data.unicef.org/resources/child-marriage-and-educati...