Not everyone that buys with credit card does so because they don't have money. Many people do this because this is the fastest way to move money to an exchange. Wire transfers to exchanges sometimes wait for weeks before they are confirmed.
No public, known, good investment suddenly becomes a bad investment in a few weeks, unless something terrible happens in between.
You must not have held gold in October of 1997. Price had been stable for years, then it dropped 13% in two months on no specific underlying news. There's tons of examples like this.