Secret Nukes were always a thing. The family atomics were used to destroy the shield wall to Arrakeen in the final siege, they don't really explain how they managed to keep them though to my rememberance. No one seems to know how to resolve the whole lasgun+shield=even bigger explosion thing though. Something I thought for sure they would have used when Harkonnen raided the Atreides occupied palace in the new movies since it happened in the books.

Either way big explosions are cool regardless of source.