BTC's sharp drop from $60K+ to as low as $50K was probably triggered by rumors that the US financial regulators are going to charge financial institutions of money laundering.
It's not the first time rumors/news like that surfaced when BTC makes a major price movement but it's still an effective way to shake the weak hands. Often times, these rumors/news are misinterpreted by the regular traders and taken advantage by big players (whales push the price down to accumulate, newbie/nood sells in panic).