Any cryptocurrency, including the BTC, has such a characteristic as the difficulty level. From this level depends, how many cryptocoins you can get per time unit. It is logical that the greater the hardness, the less the BTC you can get.
The difficulty of the bitcoin mining is changed 2 times a month. Why? It is actually very simple. Only when the BTC was created, its developers have laid in the algorithm a certain number of coins, which should be mined for 2 weeks. If for some reason miners were able to get more cryptocoins, the complexity is automatically increased, so that the mining was slower.
Now you can logically calculate – if the difficulty of the cryptocurrency mining increases, then a level of hashrate power, that is needed for producing, increases. If the capacity level increases, so the number of miners increases, respectively, more people know what the bitcoin is, and begin to show an interest to it.
This leads us to one conclusion – the more people interested in the BTC, the more growing its price. This is true for any cryptocurrency – if the complexity of the mining increases, it causes interest and the cost will increase.