WHY Bitcoin and Altcoins Falling?

Is there any concrete analysis why bitcoin and altcoins are falling? Whereas I think it supposes to be rising more just as in the financial market: the higher the demand should be higher in supply.
Back to 2009, it is unknown and that's why the price is ridiculously low then. But now that the all and sundry are getting to know bitcoin and altcoins it supposes to be rising high more and more. As at the last year 2017, it reaches 20000$/ BTC, how quickly dump to 10000$ this early year 2018 .
Please, what are your views on this cryptocurrency market trend?