Since 1601 the noble family von Eyb is owner of the castle in Dörzbach and they have been living there since then. Head of the family in 1680 was Albrecht Ludwig von Eyb, who was born 1639. In 1694 he became head of the Reichsritterschaft (Imperial Knighthood), district of Odenwald, and held that office until his death 1715.
His son Johann Albrecht was born 1669, so he was 11 years old when Johann Albrecht Matthes was baptized. He died in 1725.
Since Dörzbach was and still is a small village, I assume the Eyb family knew the local baker and eventually saw him from time to time. So taking over the godfatherhood might have been a try to strengthen the relationship to their local subjects. But this is just speculation.