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?

OKC seriously stuffed it not winning a championship between Harden Westbrook Durant.

Those three didn't buy in to win together, that is the real shame

You do realise OKC traded Harden in order to avoid the luxury tax? That's a problem with ownership, not with the front office and not necessarily with the players.

It's also pretty harsh to say they stuffed up by not winning a championship before any of their core (Harden, Westbrook, Durant, Ibaka) were even 25yo. They made it to the finals in 2012 and lost to LeBron's Miami Heat, who had learned from their loss to Dallas the year prior... that's nothing to be ashamed of.

They're tanking that's what they're doing. People don't realise how hard the small market teams in the NBA have it they're not desirable locations so can't lure top shelf FA's and they don't have the outside commercial opportunities for stars either so they've either got to overpay for mediocre stars (Charlotte with Hayward) or do it the hard way via the draft.

OKC stuffed up prime opportunity

Correct, Zodiac. Presti is doing an extremely good job of it too.

Tanking with much.

The NBA is becoming the English Premier League despite the salary cap.

People need to look at the picks they are getting.
Most of them are likely to be in the 20s and some are actually pick swaps which they may not even use if OKC is tanking.
At the moment they are hoping Houston will crash and burn, but Houston has no incentive to do so since OKC owns their picks or can swap for the next 5 years.
They also have a few of Clippers and Miami picks but both teams project as top 10 teams for the the next few years at least.

You never know what will happen in the NBA but expecting OKC to get any stars out of the 1st round picks they will be getting from other teams is doubtful at this stage.