Interesting. There was a "serious shortage" of IT auditors in 1983, too; it was a "shortage" only because Arthur Anderson started recommending that everyone ought to have a couple around the office.
The shortage entirely disappeared by 1988, and, in fact, the number of IT auditors shrank seriously from then through (apparently) now.
The new "shortage" has to do with another accounting firm over-reading the requirements of Sarbanes-Oxley to jack up their fees...
Any decent financial auditor can do this work, assuming they have a few years' experience.
You are mixing up financial auditors with IT auditors. IT auditors verify IT security and processes, et al, not audit someone's books. So the new shortage has nothing to do with another accounting firm over-reading SOX requirements.