Finn, Sheff, Cave, and Berryman

Who is John Berryman?

And what does he mean to Craig Finn of the Hold Steady (in "Stuck Between Stations"), Will Sheff of Okkervil River (in "John Allyn Smith Sails", and Nick Cave (in "We Call Upon The Author To Explain")? And why now, 36 years after his suicide?

Oh there won't be any answers here. This is just observation.