The Toronto Maple Leafs had pulled off a similar move in the past. Back in 2015, they traded down from 24th overall to 29th overall and then into the second round. This move left the Maple Leafs with Travis Dermott, Jeremy Bracco, and Martins Dzierkals rather than just the 24th pick.
This move made sense at the time, seeing that the state of the Leafs’ prospect pool in 2015 was much weaker than it would be in 2018. When the only real prospects with any substance are William Nylander, Andreas Johnsson, and Pierre Engvall, you tend to care more about quantity as opposed to quality.