Did a gun shortage create the Independence class?

Were Independence-class carriers converted mainly because there were not enough guns to complete their cruiser hulls?

Not entirely. The guns could have been built, while converting the hulls into light carriers offered a useful alternative capability.

Calling a shortage of cruiser guns the decisive cause of the Independence-class conversions goes too far. The United States could have manufactured the guns if it had chosen to complete every hull as a cruiser. Turning the ships into light carriers was operationally useful, so the conversion cannot be reduced to a lack-of-armament story. The available industrial choice and the strategic value of another ship type both shaped the decision.