The decrease in bitcoins' price is due to the growing number of bitcoin traders. Before, the price of bitcoin is constantly growing because the number of people that is into bitcoin is relatively lower. Nowadays, there are a lot of traders, buyers, and sellers that saturate the market. This leads to a decrease in bitcoin price but i think it will slowly go up.
Isn't should be the price should get high due to high demand as you have said that there is a growing number of bitcoin traders? As we all know that law of supply and demand is applied here in bitcoin the more traders/demand the higher should be the price due to the fact that the supply is just certain or is just has a limited number.