The Saints pushed all their chips to the middle of the table in 2018, trading away huge chunks of draft capital and running up their cap bill yet again in pursuit of a Super Bowl. They came (depending on your perspective) either agonizingly or delightfully close to getting to one, but then they did not.
The Saints did this because they sensed they were close, and because they knew that their window with Drew Brees was coming close to closing. After absolutely crushing the 2017 draft class, which returned them to relevance after three shaky years, they now find themselves down significant draft capital and reasonably tight on cap space heading into 2019.