Libertarians align with the left on personal freedom (Weed, abortion, relatively blind to race or sex, less foreign intervention...) and they align with the right about economic freedom.

I use to hang around Reddit back then, but I don't clearly remember. My guess is that reddit found all the personal freedom stuff appealing, while mostly ignoring of the facts about closing the Fed, eliminating minimum wages, reducing intervention... But remember that during that time (2009-2011) most of the econ talk was surrounding the bank bailouts. Ron Paul's speech was actually aligned with that of Occupy WS, since most libertarians opposed the bailouts and oppose big corporations, given that they usually lead to crony capitalism. I also have the feeling that there was less nonsense on reddit back then, but this might just be my perception.

Reddit liberals and Reddit libertarians are in massive agreement on not starting wars or locking people in a cage because they have a plant; views on economics take a backseat.

Reddit was a pretty libertarian place in the very beginning.

Ron Paul was "popular" on almost every website on the internet because his fanatical supporters flooded the web with an endless barrage of Ron Paul support. Reddit, newspaper comments, other discussion boards, polls, you name it, they were there to tell the world about Ron Paul. They were a very loud minority.

That sounds like a borderline conspiracy theory. If Ron Paul's popularity on Reddit around 2008 was a fascade, it was very convincing.

Because there were no liberals running for the Republican nomination, so many/most liberals would rather support a libertarian than a conservative.

I don't. I am not saying everyone there is liberals but most are at least from my experience.

Reddit loves 4chan memes.