Analyzing things in the Analysis forum? Well, that is highly unorthodox, but if you insist...
Hmm... So, if I am recalling correctly, in Radical Dreamers the Acacia Dragoons were stationed at Viper Manor, which over saw Gerzbuehle, which as best as anyone can figure out (especially given that Kato seems to have conceived of these locations without an eye towards Chrono Continuity) around the Denadoro Mts. Now we already know that in Chrono Cross Kato drew on Radical Dreamers for some themes, characters, and locations. Therefore, we might find some significance in the closeness of the Denadoro Mts and Radical Dreamer's Viper Manor.
That is, at the end of Chrono Trigger Guardia was overthrown and the Masamune was placed back at the Denadoro Mts, which possibly then indicates that the Masamune was placed at Denadoro specifically for the Acacia Dragoons to find. By Radius and Garai finding it, the Masamune was then transported to El Nido, where it played an important role in the events of Chrono Cross.
Therefore, given its significance to Chrono Cross, it is well within reason to suppose that the Masamune was meant to be placed at Denadoro, and the Acacia Dragoons were meant to find it, and they were meant to take it to El Nido. Which, in turn, then means that the Masamune was meant to be corrupted. Additionally, given how convoluted Project Kid was, it is quite possible that Belthasar was the one who orchestrated the Masamune's return to the Denadoro Mts and its corruption. This is supported by the oddity that the Masamune survived corruption for over 12,600 years; why would Masa and Mune just happen to fall asleep then and allow it to be corrupted? And if we assume that an external force was needed to cause this occurrence, who better to corrupt the weapon than an individual who is on par with the weapon's creator?
Further speculation: the names "Denadora" and "Doreen" are vaguely similar. Coincidence? I think so. But I could be wrong.
Yet more speculation: the Masamune and the Einlanzer have a relationship similar to that of Masamune and Muramasa (the people, not the "weapons") and their infamous (and probably mythical) competition. Except in that story, Masamune's blade was the "holy" one, while Muramasa's blade was evil and bloodthirsty. Now, the Chrono Trigger Masamune is the result of an odd English translation, but the similarities between the swords and the myth still seems apt.