I am willing to believe it was innocuous. The guy already spilled the beans and has been blackballed from government access. Does he require clandestine surveillance any more? Easy enough to get “national security” reasons why all of his devices need to be tapped. More intimidating to have visible GMen watching him for life.
For some reason this reminded me of Ernest Hemingway. In the later parts of his life, he began to believe he was being followed and tracked by the FBI, and these delusions eventually gave way to various other issues. Or perhaps it could be the other way around, but there is a catch here.
In either case this led to him being somewhat brutally treated with electroconvulsive therapy, repeatedly, to little effect beyond damaging his mind. A quote from on that was, "What is the sense of ruining my head and erasing my memory, which is my capital, and putting me out of business? It was a brilliant cure, but we lost the patient." He would kill himself not long thereafter.
The interesting thing is that the FBI was following and tracking him, and simply stayed silent as this all played out.
