Let's think about what the people outside the industry think is driving Bitcoin demand.

Here's an article from Business Insider: 5 theories bitcoin price tripled to $12,000 in three months

This article credits much of the rise to mainstream companies in the investment or payments world announcing publicly that they're "looking at" ways to use blockchain or cryptocurrency in their business. They don't mention "Bitcoin" but any positive news about blockchain or cryptocurrency is going to bode will for the perception of Bitcoin and the other major currencies.

TD Ameritrade (about to be CharlesSchwab) and Etrade both rolled out cryptocurrency futures investment options over a year ago.

Finally, this article theorizes that low interest rates is "juicing demand" by making it easier to borrow money. Their theory is logical, but impossible to draw a causal relationship, so I think this theory isn't valid.