Okay, so maybe we have the different religious groups, Spanish, KGC, Confederates, Apache, Aztec, Bigfoot, or Aliens, all possible behind the treasure. Until it's located and providence proven, any of these could have done it. But one thing would fit with any/all of them. GREED!
The Spanish and religious groups were supposed to pay a percentage to the King for what ever they "found", be it on the sweat/blood of native's backs, or captured booty. Be willing to bet, that not all that was gotten was reported so someone could have their own private stash. King's inspector coming? They would know in advance and could easily hide the extra. Bribes could have been a couple pesos, or some extra rations to those working the mines. Heck they could have even bribed the inspectors. Little bit of gold in their pockets and they look the other way. And who's to say one of the folks didn't slip a couple nuggets or some coins in their pockets as they gathered up booty. Heck they even raided each others stashes. Sea captain transporting such, you think he didn't take a little bit for his troubles? All of those because of greed.
KGC or Confederates, gold is money, and money is power. So the group grabs it, and in turn a few of the group sneak a little taste for themselves as it won't be missed, and that little bit more means more power for them. Greed again.
Apache/Aztec, gold was power. Be it monetary or religious. Buy better guns and whiskey, increase your closeness to the Gods by having more of it. So while others have nothing you have it all. All because of greed.
Bigfoot/Aliens, Well from what the ones I know have told me, for Bigfoot more gold means better cable TV and living conditions, the Aliens, they want it for fuel for their craft. Again more for them means more for them. Greedy bass turds they are.
The Government? Like I should have to explain them. They are the worst of the bunch. You think LBJ, and the rest of his gang wanted it so they could share it with the world? If so, I have some ocean front land in Arizona, and a bridge in Brooklyn that I can make you a sweet deal on. Greed at it's worst/best.
Doc and the rest of them? Come on, greed is the only thing that kept them going. Having what no one else did, and by any means.
Greed is what makes the world go round. Anything you want is greed working.
And as for maps, greedy folks aren't about to share. Last thing I would expect is someone making up a map of step by step directions to what is what they think is theirs. Somebody might steal or find it, and then they'll loose their stuff to some greedy person. When's the last time you heard of someone finding a treasure and giving it all away?
And for all of us, why do we search for this stuff? I'm pretty sure if one of us finds the big one, the rest of us will see a share of it just because you are such a nice guy.
Sure the search is exciting, it gets in our blood. But then I think of those who suffered and died for it. Many of those were innocent souls who suffered at the hands of greedy people. When i think about that, to me at least I don't want their blood on my hands. To solve the mystery would be a treasure in itself, but to hold onto it wouldn't be right. All I would be doing is setting myself up for a line of greedy folks wanting what I have. And the greedy circle would start all over again. Couple hundred years from now folks could be searching for the Lost Scarecrow Treasure. Thanks but no thanks, I'll be happy just trying to figure out where it is.