As everyone else here, I didn't know it would become so big, even though I told myself "this is the biggest invention since the Internet" after reading an article on how Bitcoin works for the third time (the first two I couldn't quite grasp it).
I had no insider information. I'm a curious person and was digging into one of my favorite forums at that time, the now defunct TalkGold - a haven for ponzi schemes and Internet scams, but also full of useful information on payment gateways, offshore structures, tax avoidance, etc. I remember I was specifically searching a better way for a remittance problem that I had, because Paypal was giving me so many headaches, when someone mentioned "bit coins" (with a space between). That was the start of it.
Mind you that in 2011, Bitcoin was already 2 years old and other early birds had had plenty of opportunity to go and grab the cream of the crop with respect of domains, which in fact they did. However, Bitcoin had just gone through one of its major crashes, and maybe because people thought the fad was over, they let the domains drop. I was an avid customer of SnapNames, buying premium names at $59.
I've never been much of a forum person but I did go to another popular domain forum at that time and tried to gauge interest for Bitcoin, and with the exception of one guy, the whole community had a negative sentiment - fad, ponzi scheme, tool for criminals, etc. The amount of ignorance and lack of curiosity in such a brilliant technology the domaining community displayed at that time was staggering, with several domainers stating they would rather put money into "prime .com equity that will appreciate in value every year" than buy $100 worth of Bitcoin.