Why is Warren Buffet's losing money in NU Stock?

 Warren Buffet disclosed that his firm, Berkshire Hathaway owns NU stock. A few months ago, Warren Buffet invested a $1billion stake in Nu Holding and the Brazilian Bank stock soared 36% shortly after Berkshire released it 13 F.  

Shockingly the stock has fallen drastically, NU stock is down 23.35 percent year to date, partly because the company reported earnings that didn't sit well with investors. Nu holding reported a loss of 0.04 per share in the fourth quarter on total revenue of $636 million.  The company also reported that it added 5.8 million customers in the quarter and now has 54 million customers. Also, the total deposit was up to about $9.7 billion.

Monthly revenue per customer: $5.6 and up by as much as 72% for the fourth quarter 2020.