Even the individual businesses (tenants of the WTC) were exposed - especially those that directed employees to remain in their offices. Many who were present in the ‘93 bombing ignored such advice and lived; others heeded it and died. There was probably no end to the potential defendants in the case.
You’re “prolly” correct on that point and the litigation would still be on-going to this very day.
I do recall the feverish discussions here about using using tax dollars in this manner, post 911.