People say love is the most powerful force on Earth, and if that is the case, then the lure of money is an extremely close second. The Beale Papers basically gave an open invitation to a $20 million treasure (over $500 million in today's money!) just with a catch-- decipher some unbreakable ciphers. With that much money at stake and enough desperation, no task seems too large.
I agree with Singh's conjecture that the entire story could be a made up ploy to profit off other's greed. If this scenario were the case, the anonymous author would be humored to learn that in the 21st century, there are still individuals attempting to break the Beale Ciphers.
If professional cryptanalysts have been unable to decipher Beale's message, what would cause the average Joe to believe he can? It's not only the desire to find a gigantic sum of money, but also lust to be "first" or "special" or the best at something. One may be thinking If I decipher Beale's code, I'll be rich, AND everyone will know me as the smartest person ever! In addition, people often have a heightened sense of themselves, especially their personal skills. As a result, you get amateur and probably first time-codebreakers undertaking a task far beyond their abilities. It is important to realize when something is outside your limits. You can't do calculus before knowing how to add, you can't run a marathon without knowing how to walk, and you certainly can't break an "unbreakable" cipher without extensive knowledge and practice with the subject.