As far as I know, demand on the market controls the price of Bitcoin. It may sound like a too classic reason but in theory it is also the most realistic reason.
In most cases, supply and demand play the big role inside this market. The more
buyers the more chances to grow in value. Lesser the hold and more sell demands
the cheaper the price to expect.
Look, if there is positive news, many people want to buy Bitcoin, then the price of Bitcoin will be increasing. While if there is a negative issue, people are trying to sell their Bitcoin, then the price is decreasing. This means, the demand really influences the price, while the demand is influenced by the news/issues.
News affects those who are just riding but for those who understand the market it
won't affect them, knowing that bounce happen after.