A Tether official and the head of the world’s largest crypto exchange grew alarmed that Sam Bankman-Fried was trying to destabilize the stablecoin and with it the broader crypto market last month in a last-ditch attempt to save FTX, according to messages seen by The Wall Street Journal and people familiar with the situation. In a Signal group chat called “Exchange coordination,” Changpeng Zhao , the chief executive of crypto exchange giant Binance, confronted Mr. Bankman-Fried on Nov. 10.

---