Just like the carnage in 2008-2009 (although big banks have been spared) lots of traders, prop groups, hedge funds, and black boxes have blown up or closed down these past 2 months. It's never a good idea to treat your unprotected trading account (at a clearinghouse) like a bank account..always keep the minimum required amount. One or two rogue accounts can take down an FCM or clearinghouse and all of its trader clients (see Ronin Capital). CME also learned its lesson from the MF Global debacle.
Or maybe they learned they gonna get sued