It seems natural that certain people who are anti-government and/or very privacy-conscious would be driven toward Bitcoin. There are other coins that are more focused on anonymity, but none gained the reputation and trust of Bitcoin, and Bitcoin also gives an interesting mix of both respecting privacy and promoting transparency.
I'm not a fan of Assange, Snowden, and other similar people, primarily because their distrust for the US seems to match their sympathy toward Russia, an authoritarian regime waging wars against other nations and oppressing its population.