The economy went to hell over the deaths of 2,977 people + 19. Not even to save them, in reaction to their deaths. Recently, the economy also went to hell over the deaths of no people. Throughout history, economies have been ruined over the deaths of a single person (if they are important enough).
Why are you so certain that if we had done nothing, that the economy wouldn't have cratered anyway? China closing negatively impacted US businesses. Europe shutting down, which they would have done, would have further negative impacts. Our "cheap" manufacturing centers in places like Bangladesh, Malaysia, Indonesia are going to be affected like China was, in the future, and likely with more death. Why would the US economy remain strong when so much of it depends on demand from the rest of the world?