It is not an agent success though... The Sixers are a contending team, but in order to go to the finals, they have to pass over the Bucks... To do that they need far more than Embiid and Simmons and they already lost Butler and their best shooter on J.J Redick...
They therefore had to pay Harris in a luck of an alternative answer after the Bucks extended Middleton and also had to to pay and add Hortford in a desperate hope to avoid this happening on the floor when they meet the Bucks next:
In short, one can safely say that "because the Bucks are after winning the title, everybody else is trying to buy their respective chances (the Lakers, Clippers and Rockets circuses, even more so than the Sixers or the Nets)!