What if Deltarune was the PREQUEL to Undertale?

See, I think the reason the whole war started was because of the roaring, causing the humans and monsters to split apart and begin the war. And I know that Deltarune is the alternate universe of undertale, but I dont believe it one bit. And the fallen humans are descendants of kris. And their traits were inspired by the flowers in Chapter 5. This could also explain why sans said something about not wanting to go back anymore, as the result of the war was the roaring, and none of the monsters wanted to relive those moments.