A short position means that the trader was betting on the price of Bitcoin $BTC decreasing.
When the price moves against the short (in this case, it increased to $94,570.90), the trader is forced to close their position to prevent further losses, leading to liquidation.
The amount of $50.4K could refer to the size of the short position, the loss incurred, or the value of the liquidation.

BTC
77,594.74
+1.81%

ETH
2,331.74
+2.67%

XRP
1.3938
+0.95%