Chinese demands because their current economic crisis, plus news of brexit, plus immediate arrival of the block halving date, plus the generated hype. I'm pretty sure those are the reasons why the price is surging like mad. Could be wrong, of course.
It's basically just this.
There are a lot of investors, speculators, day traders, whoever, that are all looking at Bitcoin right now and considering how valuable their investment is, calculating the risk of investing now, and everything else.
Everyone is taking a calculated risk, and those that buy in because of some crisis right now might actually stay in for a while.