You forget that all universes and dimensions are held in the Void. Destroying one wouldn't destroy another, or a future being. Since time does next exist in the Void. If it did, and your logic was true, Life would already be gone. Since Gavla has already crushed the universes that came before his own. Some people forget what Death said to Gavla in AVID. That in the future his hands will be covered in the dead of trillions. That sentence has come true. Multiple times, probably. Comic- The Launch Also, none of the shown Gavla(s) are the same. Life isn't the same as Dead Gavla, and Goggles is a completely different one. There is only one thing connecting Life and Dead Gavla. Life's body was the one MG took over in AVID. We saw Death move the body. We also already established that in the comics.