The meaning of the expression “all hanging together” is that our only hope is to combine our resources because we are already doomed as individuals.
It’s a quote from John Hancock, who was the first to step forward and sign the American Declaration of Independence.
He said to those gathered, “We must all hang together; else we shall all hang separately.”
And the hanging he was referring to was death on the gallows for treason.
That is why when embarking on a difficult project, does a group say they must “all hang together”.