> perhaps everything behind the scenes could fall apart

The problems in the world that would result in the entire top line public companies falling apart that make up the TSM or even S&P 500 fall apart protractedly - not like a few companies getting knocked out and replaced by others but the _entire concept_ failing - would be of such magnitude that people's retirement savings would probably not be the 20th thing on their list to worry about. Look at how COVID even at its worst could barely knock things down more than 25% or so for a few months.