Crypto experienced one of its worst days in years on Aug. 5. Few saw it coming, but traders’ addiction to leverage has been quietly amplifying marketwide risks for months. If leveraged trading was the kindling, the Japanese yen’s abrupt uptrend was the match. Thankfully, the fire may burn out as quickly as it started. Surging costs on yen-denominated loans caused the crash. Now, markets are set for a healthy rebound as traders finally pare back leverage and exposure to the yen. If broader markets stabilize — and they probably will — crypto may soon make a comeback. Bargain-bin borrowingIt’s no…