It's like a destructive virus in a complex computer program you wrote. The program is running, but it is gradually destroying itself. You like some parts of the program, so you quickly go in and save these parts, copying them to a different drive or something.
God is saving us. But some of us don't have faith in the salvation. The virus already got to those who reject salvation. Some of these reject God entirely. Because of the nature of the program of the universe, anybody who rejects Jesus-salvation will go down with the program... the destruction of the universe. Remember that at death, as far as any of us are concerned, the universe is gone for us, the dead, even if it remains for a while for the living.
God is-making/has-made a new program... a new universe. Those of us He saves will go to that new universe. Those who reject salvation will go down with this universe, which will become the lake of fire.