Google "Andrew Left citron research evergrande". He explained it all in 2012, was banned from Hong Kong trading for 5 years as a result, just when Evergrande finally grew its ponzi scheme too big.
Long story short: the head of Evergrande was politically connected, helped build China on borrowed money, had no credible plan to ever repay all these loans, one day China decided to stop leveraging and Evergrande had to unwind... except it couldn't because it didn't have enough actual money to repay loans quickly. Too bad their bonds were sold to everyone and their grandmothers in China to try to find yields in the no-interest environment. Now that interest rates are back, nobody want junk Evergrande bonds anyway. Catch-22.
Long story short: the head of Evergrande was politically connected, helped build China on borrowed money, had no credible plan to ever repay all these loans, one day China decided to stop leveraging and Evergrande had to unwind... except it couldn't because it didn't have enough actual money to repay loans quickly. Too bad their bonds were sold to everyone and their grandmothers in China to try to find yields in the no-interest environment. Now that interest rates are back, nobody want junk Evergrande bonds anyway. Catch-22.