Once again, Jack was NOT blown up. He was in an elevator that crashed and died due to the injuries from the crash.
Also, Hope was "killed" when she was in a cage that dropped into a vat of acid, yet she's still alive and well (it was explained that because Ernesto was a magician, it was just an illusion). So even IF Jack had been "blown to smithereens", they'd find a way to say it wasn't real, or it wasn't him.
And once again, I don't understand why you think it's such a big deal for a dead character to be resurrected. The soaps have been doing it for decades now. No matter how a character died, with a quick rewrite, they rise from the dead. Even if it's with the line of "it didn't take."