Because for is coming everybody investing in Bitcoin to get free Bitcoin Gold coins. Yesterday we had bitcoin for less than 6k, today is going straight up, all analysis saying we can reach 7k before fork which is planned on 25th of october.
Also capitalization of marketcap is going up from week to week, right now we have $173 596 177 301 in market, and already 1183 different cryptocurrencies.
Hope we will see soon Bitcoin for 7-8K!