You're conflating the solution with the methodologies, which is what the article is listing in the original quote. The rest of your response is predicated on this mistake.
You have to tell me more. Which part of the text you quoted you think is not true?
That various people attempted to decipher it? Or that they were missing a crucial hint? Or that they tried the listed methods?
The quote is not claiming that these are the only methods people tried.
Sure I can simplify it. The article claims an important hint was missed. A hint, not the solution and not the key. Then lists the “methods” that people have tried and presumably missed, which of course is not true. You’d get this when you read all sentences together as a whole.