The deal is, at least it used to be, that those people who became CPA's and worked for significant firms worked their butts of for a number of years auditing major clients. Then, often , those CPA's got to know the client's business rather intimately. Next step? Quit the accounting firm and go to work as CFO etc for the client. In those days Accounting firms were partnerships. Become a partner and you had it made. Think they are now mostly public corporations.

Steve