[salawat]

The implication in the letter is "if you go forward with Libra, then scrutiny will increase." Which again, makes sense, because previous safeguards (KYC and AML) would have to be updated to reflect the realities represented by financial transactions in Libra.

The financial system is regulated through high barrier entrance controls, and various levels of traffic pattern analysis through AML laws. Libra threatens to blow a hole in that for some period of time while the tools and processes are updated. Therefore... More scrutiny.

It isn't a conspiracy. It's just how things work in strictly regulated industries. Although usually, it isn't such a big deal that Congresspeople get directly involved through constituent outcry, and it is left to the Executive agencies to do the back and forth with the industry to ensure things go without a hitch.