It all depends on the hype, bitcoin always gets hype periods. Back in the first days when it reached to over 30 dollars it was due to couple hundred of few thousand people interested in bitcoin then a hype happens and there are thousands more interested in it and buying it and that increased the price a lot.

However, the second one in 2014 was dude to us reaching to mainstream media and almost everyone hearing about at least "what bitcoin is" even if they are not interested they at least heard about it in 2014. The latest one was "bitcoin is going up and making everyone rich" and people went into bitcoin and realized they were a bit late and they kept buying bitcoin to go into many altcoins and ICO's to make money. I don't know when the next hype will happen or how it will happen but when that happens it will be pretty quick to reach new ATH prices.