Idk why people are confused by this. Betty and Archie made out on top of archie’s bed but hiram placed a bomb under it. The bomb exploded but instead of dying, the timeline stopped and we were transported in a parallel universe where everyone is mad, the devil exists and lallorona steals babies for real. So to get out of that universe, jughead concocted a plan to recreate the chain of events that led them to riverVALE and it worked. Fake jughead warned betty and archie and they made it out alive; Oh and everyone gained superpowers when they went back to the first reality but that’s irrelevant. Ergo facto, blow up a bomb while barchie make out and it’ll solve all of your problems!!! 

i hate HATE that riverdale is riverdale where you can’t dismiss anything because i need to understand why people would think the show would ever revert back to 5x17 for any reason other than ‘we want va/bh back and barchie gone’