The problem is, you've got to get their attention amidst the background noise of thousands of other fortune tellers and shamans. In that letter, claim that all other Advisors have rock salt for brains. Brag on your own successes as Prophet. Convince the reader that you have an Inside Track To Special Knowledge. Only I can save you.
Many wealthier folks are perhaps even more worried.
These people are fine prey for Advisors, who've brought their usual techniques into the fray because they work. For years, his primary source of income was investment advice and newsletters. That rascal almost talked me into becoming a survivalist during the Carter adminstration. It was my dear mother who beat sense into my head, and of course, his predicted collapse never occurred. Fortunately, their respective egos are probably too large to permit such a marriage.