Cavs, Bucks, Sixers all stink and they need a franchise player.
This may be only time they can all get one in the same year.
This is true. Cavs have Irving who is an all star. They need a rim protector. Theory is Favors, #5, and #23. They do it because they get their rim protection, and another potential all star @ 5. We do it because we get Wiggins.
Bucks need a rim protector since Sanders is up in smoke. They have a promising SF in Giannis, but they don't have any pieces on their team that would justify them moving back. They don't have enough clay to build with, and since the hardest thing to acquire is franchise talent, they're staying put.
Sixers have MCW, Noel, and Young. All are, or will be decent, but none will be great. They're staying put, unless they decide they don't want anyone but Wiggins, and there #2 option is Vonleh or someone who could be had later.
Ironically, I could kind of see the Cavs trading the pick. It seems like something they'd do. But then again, I doubt it. If Wiggins or Embiid turned into franchise players, and they traded the pick, there would be riots in Cleveland.