Well, there are at least 3 very logical reasons for that:
1) If you hvae been watching the order book trades in the spot market, in Binance for example, for the past 2-3 days, one could see a big sell wall of 6 million usd at the 12K usd price level.
2) We need to retest the 10K price level. Remember previous resistance now becomes support. We migh be seeing 10K as support several times.
3) The TD Sequential indicator needed a reset to No. 1 and with this fall we can rise again.