If they thought that they probably wouldn't be publicly traded companies. One of the big reasons for publicly traded companies is that it limits liability for owners when the cards inevitably come tumbling down. The structure is set up to cushion failures and redirect money to new ventures as times change.

Humanity has been watching companies grow and die for longer back than we have preserved written records exist. Our entire system today is built with the recognition that these things don't last. The execs at these companies know that as well as you do.