please give me a short description about SVB collapse

Context: On Friday, March 10, 2023, Silicon Valley Bank failed after a bank run, marking the second-largest bank failure in United States history and the largest since the 2007–2008 financial crisis. It was one of three March 2023 United States bank failures.

Answer: It's due to risk mismanagement of SVB Bank, where the bank bet on long dated treasury bond. When the bank runs happen, SVB don't have a choice but to sell those long dated bond at a steep discount and incur huge lossses.