Accidents happen when multiple factors combine. Lets say that there is 1:1000000 chance of engine failure during those 15 seconds. You get multiple warnings, you forget to turn on transponder, you start to descent, nobody know where you are, TA/RA is not working in other aircraft and just happens A380 flying 1000 ft below you. 500 lives lost just for turning transponder to STBY.
Not to mention the system chaos as one momentarily selects several different TXPDR codes whilst changing the squark, activating a whol lot of flight plans.
