I think it's a combination of Danny finding players and Stevens getting the most out of them. CBS has done an excellent job giving these guys opportunities and putting them in a position to succeed. And Danny has shown he has an eye for guys with talent who've been under-utilized by their former team and are available at a bargain rate.
Just think. At the time many people, including me, derided the Rondo trade. We were shocked that Danny Ainge, a man famous for his ability to make great trades, would take so little for Rondo when he got so much for KG and Pierce. But here we are three months later and it's clear as day he won that trade too. A guaranteed 1st in the 14-20ish range, what will probably become an early 2nd and a mid 2nd (Although I wouldn't sleep on the wolves, especially if KG comes back in any capacity, they prob won't make the playoffs next year, but Wiggins is legit.), 2 trade exceptions and Jae Crowder. No one heard of him before, but now he's a key part of why we've been playing so well, and would be an great role player for the long term.
All for a surly, unengaged, one foot out the door half-season rental version of Rondo who hasn't made them any better if he hasn't made them worse. Amazing. And we had to drag Prince to play for us, he wanted a buyout from the get go. But he played well with this group and Stevens and Danny managed to turn that into Jerebko and Datome!
Since the rebuild started, Danny has just been incredible. I am genuinely excited to see what him and Stevens can do together in the next few years. It's gonna be good.