Unlike many other birds, ducks are precocious.  Wild ducklings provide all of their own food.  Yes, they follow their mother in a cute line, but she is foraging for herself, not her ducklings.  The ducklings fend for themselves.  The mother provides them with preen oil and a warm place to snuggle at night.  She does not teach them anything.  This is why the life expectancy of ducks is so low.
The life expectancy of a wild duck is just under six days.  Six days.  Meaning that more than half of the ducks that hatch into this world will leave it before they are a week old.  Some survive, some die.
https://www.ducks.org/media/Conservation/GLARO/_documents/_library/_research/Duckling_Survival.pdf
Some animals, when raised in captivity, do not have the skills to survive in the wild.
Wild mallards do not learn much from their mother, and therefore are not lacking in the skills that they need to survive in the wild.