I've had a long running pet theory that while the trolls aren't the villains per se, they do want to have Kristoff hooked up because he's part of their family.

I've had a long running pet theory that while the trolls aren't the villains per se, they do want to have Kristoff hooked up because he's part of their family. This part of the song is particularly telling: /// So she's a bit of a fixer-upper, that's a minor thing Her quote 'engagement' is a flex arrangement, and by the way I don't see no ring! So she's a bit of a fixer-upper, Her brain's a bit betwixt Get the fiancé out of the way and the whole thing will be fixed /// With that said it doesn't quite jive with Hans' betrayal (you could argue the Trolls made him do it but there's no support for that claim). But I think there was a potential to find out that the Trolls were manipulating things behind the scenes to get Kristoff and Anna together.