No one took the ransom note seriously. Firstly, the Ramseys. The note said don't dare call the police, so the first thing they did was call the police. Secondly, the police. If they had believed the note and the "foreign faction" stuff they would have called the FBI immediately. Thirdly, Lockheed Martin etc. It seems they thought it over and decided there was no real threat. Fourthly, the public. When the note was made public *everyone* with the slightest sense knew it was bogus. It is so transparently bogus that we need not wonder at all that no one followed the protocols of a real threat. I'm not surprised that the Ramseys called the police or that Lockheed didn't sound their alarm bells.
But it is precisely because it is so plainly false that such a note can yield so many useful clues. Yet, here we are years later, and we cannot answer some simply questions, like - what exactly was the purpose of the note? What agenda did it serve? What part in the crime? For example, was it supposed to draw attention away from the body, to lead the police away from the house, have them running all around town? Was it intended to delay, to buy time? Or just to obfuscate, distract, obstruct? Was it intended to incriminate someone? (I tend to this view) Or was it a "message" to John Ramsey, payback of some sort, an extra cruelty? I don't think any of those questions are settled, let alone the question who wrote it.
There are some questions that can be counted as settled though. Chiefly, we can say - for sure - that the note was *not* written by a random perp. It was written by someone who knew John Ramsey. We can say that for certain. So we can forget about all versions of the random intruder theory. A random intruder did not write that note. (This is not to say that a random intruder did not kill the victim, but we can say 100% certain that a random intruder did not write that note!) That narrows it down from about 250 million people to about a dozen or so.