>>716222279
In Undertale, Frisk barely knew Toriel and doesn't have to be her child, and Sans is nice to the kid and sees her as a friend. Asgore is a child murderer and her kids are dead, so Toriel moving on feels like a good thing for her.
In Deltarune, Toriel is Kris's mother and recently divorced. Her kids are alive so the audience wants the family to get back together, we don't know why she hates Asgore, too. Sans is also antagonistic to Kris's.
Toby is a master at making you feel different by simply changing the point of view and context.