Since the announcement of the cancellation ppl are using their bitcoins to buy altcoins, that's why the price decreased (and not plummeted, it is still 7138$ right now). Look at the long run. I still believe bitcoin is the safest crypto to invest in though the cancellation of the fork will definitely benefit the altcoins in the short term
The drop of the price due to the network congestion. So until after the congestion problem is solved, the price might stay here.