In the past few days, btc has been hovering around 7800 usd, and all the altcoins have begun to rise. What is the reason for this?
Such things happen for a shorter time. Bitcoin always leads on change on every bull and bear market and as its price gets stable, rapid change starts in altcoins. One of the reasons for it might be the bitcoin acting as the main currency pair. When bitcoin is increasing, people don't buy alts with bitcoin but while it gets stable, they start buying altcoins and vice versa.