Whether Satoshi sat down to create an explicity weaponised technology is up for debate.
Sure, there's a bit of room for ambiguity, but not much:
While the security technology is very far from trivial, the "why" was by far the biggest stumbling block -- nearly everybody who heard the general idea thought it was a very bad idea. Myself, Wei Dai, and Hal Finney were the only people I know of who liked the idea (or in Dai's case his related idea) enough to pursue it to any significant extent until Nakamoto (assuming Nakamoto is not really Finney or Dai). Only Finney (RPOW) and Nakamoto were motivated enough to actually implement such a scheme.
The "why" requires coming to an accurate understanding of the nature of two difficult and almost always misunderstood topics, namely trust and the nature of money. The overlap between cryptographic experts and libertarians who might sympathize with such a "gold bug" idea is already rather small, since most cryptographic experts earn their living in academia and share its political biases. Even among this uncommon intersection as stated very few people thought it was a good idea. Even gold bugs didn't care for it because we already have real gold rather than mere bits and we can pay online simply by issuing digital certificates based on real gold stored in real vaults, a la the formerly popular e-gold. On top of the plethora of these misguided reactions and criticisms, there remain many open questions and arguable points about these kinds of technologies and currencies, many of which can only be settled by actually fielding them and seeing how they work in practice, both in economic and security terms.
Here are some more specific reasons why the ideas behind Bitcoin were very far from obvious:
(1) only a few people had read of the bit gold ideas, which although I came up with them in 1998 (at the same time and on the same private mailing list where Dai was coming up with b-money -- it's a long story) were mostly not described in public until 2005, although various pieces of it I described earlier, for example the crucial Byzantine-replicated chain-of-signed-transactions part of it which I generalized into what I call secure property titles.
(2) Hardly anybody actually understands money. Money just doesn't work like that, I was told fervently and often. Gold couldn't work as money until it was already shiny or useful for electronics or something else besides money, they told me. (Do insurance services also have to start out useful for something else, maybe as power plants?) This common argument coming ironically from libertarians who misinterpreted Menger's account of the origin of money as being the only way it could arise (rather than an account of how it could arise) and, in the same way misapplying Mises' regression theorem. Even though I had rebutted these arguments in my study of the origins of money, which I humbly suggest should be should be required reading for anybody debating the economics of Bitcoin.
