They'll probably need 10,000 or so to unravel a certain individual's scams on his returns but still, a cursory look at why they are (allegedly) employing them.
https://www.nytimes.com/2022/11/06/us/politics/irs-agents-fact-check.html
https://www.cnbc.com/2022/08/31/irs-is-not-hiring-an-army-of-auditors-whats-really-happening.html
I'm sure there are many other sources that will contradict the information above but which outweighs the other I wonder.