Picks gave them three (eventual) MVPs in the past...
The interesting thing for me is that knife edge between contending and rebuilding. They were a solid team last year and some improvement from younger players and/or a free agent could've lifted them a spot further.
But they were also one of the most expensive rosters, ahead of the Warriors, Rockets, Lakers, etc. They might've figured that any improvement from their prospects would've been counteracted by a decline from veterans, and that it was best to sell a few guys high (CP3 went from an undesirable contract to in-demand-piece).
Their biggest contracts were Paul, Adams, Gallinari and Schroeder and they've shed all of them. They took on Rubio, Green and Oubre and offloaded all of those also.
Picks are a way to time your incoming talent and negotiating power to suit your window of contention. Free agents aren't going to seek out OKC for the lifestyle and commercial opportunities... Horford will be a practical piece, and they have 2-3 decent options to start with him. Struggle through next season until the drafts are stronger and then improve via a mixture of drafting with picks and trading picks to get acquisitions over the line.
From 2007-2009, they drafted Durant, Ibaka, Westbrook and Harden - an amazing run.
From 2013-2017, Denver drafted Gobert, Jokic, Murray and Mitchell.
In 2014, the 76ers drafted Jerami Grant, Elfrid Payton and Joel Embiid. Added Simmons in 2016 and had the first pick in 2017 also.
What other teams are setting up as effectively to tank alongside them?