People are bombarded with so much marketing, they need to be reminded of the brand close to the purchase decision so that the brand’s mental associations can work their magic. This is why short-term activation media are widely used in conjunction with media that build predisposition longer term. Brand building media put the ball in the vicinity of the goal and activation media head it home.

The Meaningful Marketing Measurement 2021 report by the DMA showed that campaigns designed to build the brand AND activate a response have a greater impact than campaigns designed to perform just one of these roles. The Long and the Short of It by Binet & Field reaches a similar conclusion.

Here are some videos/animations designed to explain the concept in more detail:
A video clip from YouTube
A 1-minute animation
A 6-minute audio clip from a podcast