Holder is not on this letter. And the letter was sent to the CFPB. Holder never worked at CFPB, which has very different jurisdiction than the DOJ. So what exactly are you alleging?
I'll take a wild guess that he is alleging that Eric Holder's failure to prosecute any of the CEOs of the financial institutions that played a critical role in the financial crisis (by, e.g., making loans to people without incomes, packaging the loans into mortgage backed securities, and passing the resulting time bombs off to other parties) was appreciated by his former and future colleagues at Covington and Burling and their clients in the finance industry. That Eric Holder was very aware of that appreciation and anticipated that he would be rewarded for it.
When party A sells party B a crappy product with overinflated promises, the result is a civil suit, not a DOJ criminal prosecution. In any event, what does Equifax have to do with that? Was Equifax rating mortgages or something? Is it a bank?
When the creation and representation of crappy products entails fraud or other crimes the result would actually include criminal prosecutions by the DOJ (in a world where the DOJ weren't captured by party A's industry). Tying the two scandals together is the influence of the finance industry on regulation and enforcement through the revolving door, in both cases to the same law firm representing financial institutions.
Fraud can be either civil or criminal, depending on the circumstances. Where sophisticated parties are on both sides of the transaction, and the allegations of fraud boil down to complex questions regarding representations about the product, it's a civil matter, not a criminal matter. The fact that the DOJ correctly interpreted the law instead of trying to satisfy peoples' bloodlust isn't a "scandal."
I am alleging that this company is expert in hiring people from government agencies who had in some way to do with financial regulation. That's all. You can draw your own conclusions.