Landscape

The castle(s) really add a sense of scale to the massive landscape!

Yes, they really do not look large unless you zoom or stand right in front, any yet they are huge compared to previous original medieval structures.

Have you known, Ludwig built Neuschwanstein on the ruins of two castles, bridging a natural gap with modern means? It once was the site of Hinterhohenschwangau and Vorderhohenschwangau, two simpler fortified towers long in ruins and his dad Max had already turned the one closer to his own reincarnation of Schwangau castle into a sort of private romantic picnic place dedicated to his wife. Ludwig gave order to level mom's most beloved landscaped overlook as he thought hurting and punishing her, who had some difficulties to get along with Wagner and genral critique about his genious and his lifestyle, would be a fun idea, and as he was at it, he decided not to build not just a showy roofed and heatable pavillon on the devastation to invite his favorite musician over for a coffee as was the initial idea but a better and bigger castle than that of belated dad below. And for that he just needed the place of both ruins and the gap. -- LOL

This is a tale used in novels that seems more backed up than others surrounding the "Kini", simply for the Wagner clan was in possession of a letter that tells most of it from his own hand , how he planed in 1868 a homage to his idol as a respite far from his mothers "defiling prose" for both of them and promised him a private apartment in the new castle, to be ready in 3 years.
Of course, in 3 years nothing was ready at all and personal wishes started to change anyway...

The underlying true main cause was probaply that when humans are overwhelmed by their stupid everyday reality they look for ways to escape and often anoy their folks in the process. It needs not to be things officially declared to be dangerous drugs. Some turn their car radio loud and drive around sans purpose, some go to town and shop for fashion 'til they drop, some buy and eat copious amounts of icecream, some collect pulp fiction magazines or attend role game conventions in ridiculous costumes -- everybody has to have their personal reward zone, and generally it's just fine.
Ludwig was just like all of us but then he was also a king so he had XXL mechanisms to match when things did not go his way. He sponsored new operas on old tales and planed huge architectural projects inspired by them, and he pined for an unreachable elder guy he felt was a genious, spoiling him rotten -- just to escape and feel good.... LOL
But of course his letter to the admired Composer was just about the results of the mechanism, not about itself.

The conspiracy theories about the king's death however are many and there where better precautions taken so we will never know anything as detailed and for sure as about how Neuschwanstein was concieved. :o(