This Parallel Universe had many differences from the DC Universe. For example, this universe had neither Satan nor Gabriel. Otherwise, Earth would not have fallen to the Zerg so easily.
Why did Andrew know? Because after arranging everything, he summoned Scumbag Kang and asked about the gods and demons.
Scumbag Kang had countless enemies, so his whereabouts were always uncertain. Alice spent quite some effort finding him and bringing him to Wayne Manor.
"Satan might have existed before, but he definitely doesn't exist now. The strongest in Hell at present is Trigon, along with several other Demon Kings. I've dealt with quite a few of them, and we're on fairly good terms."
Scumbag Kang smoked as he said, "As for Gabriel, I've never seen him. The ones in the churches are just ordinary Priests."
"Fairly good terms? The kind where they can't wait to kill you?"
Andrew sneered. Looking at Scumbag Kang, he said, "You only have one month left to live. You should start thinking about how to survive."
Cough, cough, cough. Scumbag Kang coughed repeatedly. Wasn't he here to answer questions? Why was Andrew suddenly telling him he only had a month left to live?
Scumbag Kang asked, "Is that real? Did someone Curse me?"
"You've been cursed by cigarettes. You smoke several packs a day. If you don't die, who will?"
Andrew looked disgusted. Scumbag Kang stared at the cigarette in his hand, speechless. I'm Constantine. Even Demon Kings can't kill me, but I'm going to die from a lousy cigarette?
Scumbag Kang wanted to toss the cigarette away, but after hesitating, he continued smoking. It would be a waste otherwise. He asked, "Uh, how did the me from another universe survive?"
"In another universe, there was Gabriel and Satan."
Andrew explained the plot of the movie