The impact of a smash cut is strengthened when it juxtaposes two scenes with wildly different tones. For instance, horror films often use the jarring nature of a smash cut to transition from a gruesome in-progress murder scene to a happy or peaceful moment. (MasterClass)

If you’ve got a loud scene that immediately goes to a quiet scene or vice versa, this is where you’d use the smash cut. You want to use it when you’re transitioning between two completely different scenes, emotions, or narratives and you need to make an abrupt transition. (Pond5 blog)

Suddenly, there is a visual and an audio smash cut to introduce Samuel L. Jackson’s character: the visual smash cut is created by going from the girl dancing, with music background, to a close up of a clock. (Introduction to Film & Media Studies)