That's how they killed him.
Perhaps you're right..... "They" may have drove Roger Craig to suicide but he committed the act. This is exactly what I think happened to George De M ....
In some circles of society there is a creed of "death before dishonor".... And I believe George De M was of that creed. De M knew the truth about the coup d e'tat, and he knew that Lee had been made the scapegoat....but he couldn't tell the truth to the whole wide world because he would have been putting a noose around his own neck and bringing shame to his kids and grandkids.