The article calls out, multiple times, that the reason people were fired (all 24 of them, with another couple hundred contractors being flagged) were because they were moonlighting. It says nothing about their performance, except in the vaguest of terms ("weren't logged into the VPN enough" for instance), and the fact they were initially flagged to be investigated (presumably because of performance, but again, no details; certainly nothing to differentiate them from the 975+ that were investigated and not found to be moonlighting).
Which is an interesting admission on Equifax's part. An investigation of over 1000, including interviews and the like, literally thousands of man hours...to find 24 people who had jobs on the side, but whose performance wasn't poor enough to warrant being let go in and of itself.
Tells you something about Equifax's priorities.