I think the main issue that can bring bitcoin price down is negative news about regulation.Many times negatives news about bitcoin regulation and all that news is not true or false news. Negative news bring people become panic and they selling their bitcoin and that causing bitcoin price drop
There are many factors can be the reason why the bitcoinprice fall down. I think one of the biggest reason could be the bad news regarding bitcoin like, bitcoin scams, bitcoin scammers, bitcoin thieves and so on. I guess these things contributed a lot to the bitcoin price fall down