Some experts think that till the end of this year the price of Bitcoin will be 15000$. May be they have a lot of Bitcoin and just want it. That is why "predict" it

Exactly. Many predictions just express the desires of these predictors. But neither these predictions, nor desires do not affect the market.
Some believe that until the end of the year, the price may fall to a level of $ 1,500, others believe that the price may rise to $ 22,000 this year.