This incredible rapid increase in bitcoin's price was due to the wide acceptance of bitcoin, thus, increasing demand dramatically. Since the announcement of Japan that they will accept btc as a mode of payment, many had gained interest in bitcoin and currently, Australia also announced their acceptance of crypto currency. Hence, the rapid increase in bitcoin's price is not so surprising.
Those were the days. This old thread has one very important lesson to give us. And that is Bitcoin moves and grows beyond our expectations. When Bitcoin started, it was considered very high already for it to reach $5. But then in the end $5 was proven to be so low a price prediction. Here, in May of 2017, the speculation was very little for Bitcoin because it was almost absurd to think that Bitcoin will be reaching as high as $6,000 in December of 2017. $6,000 was considered a very ambitious target back then. But then for the nth time, Bitcoin proven everything wrong because it even went as high as $19,000 in December.
Exactly,right now i cannot imagine if bitcoin drops to 6k, on august i also thought that we will end at around $8k and reaching $20k will be months or years away but now most of investors predicts that we may see the price as high as $40k. I hope they are wrong again andbitcoin exceeds expectation.