that is a guess
True. But an educated one. After Lehman, Merrill was getting ready to fall, then Goldman, then AIG. You lose two more investment banks, the worlds largest insurer and trillions more of wealth and there would have been panic. And that doesn't take into account all the hundreds of other smaller banks that would have been impacted by the big boy contagion. TARP and the capital injections showed the world that there was a solid backstop and it stopped the panic.