For example, another story.
From a purse or exchange ETH is stolen. In order to quickly make a profit, scammers urgently sell it at a price lower than the market price.
And so the price falls on the ETH.
The amount of ethereum stolen will need to have to be huge in order to make the price of ethereum to go down, so that is not really a good example, what causes the price of ethereum to go down over the long term is that as scammers become a greater part of the community people begin to lose confidence in ethereum and despite its great technology no coin can survive if it doesn't have the confidence of the people that use that coin.