I think Linux users are humans with a range of interests.

I'd say 2009-2012 it was mostly Linux users, at least the communities I was in.

The original bitcoin software ran on Windows if I'm not mistaken, so I don't know about "mostly Linux users".

Maybe it was different in the US. In Europe I get the impression the FOSS community is predominantly left-leaning. My local Debian community certainly is, and they're anti-cryptocurrency (like myself).

Slashdot was also quite skewed against bitcoin, and that was a pretty international geek readership.

I know a gui for bitcoin core was available for windows machines by at least the end of 2010 as that's what I used when I was first reading about it.

It was mostly hackerspace/linux kind of people back then.