Why did the AFL feel threatened by the rise of the CIO?

Many couples delayed marriage - the divorce rate dropped sharply (it was too expensive to pay the legal fees and support two households), and birth rates dropped below the replacement level for the first time in American history. Families suffered a dramatic loss of income during Herbert Hoover's term in office.

So, I think the answer is that t he founder of the AFL left that organization and went on to establish the rival union, the CIO.