Yes it was, the only question is if they can prove it. Puff put a hit out on Tupac, Orlando gets stomped out, the Crips ask Puffs man Zip if the hit is still valid, he says yes and provides them with a gun, they roll up on Suge and Pac and shoot them, Tupac dies, Puff pays Zip a million dollars for the hit, Zip keeps the money and dies.
So what might protect Puffy is that almost everybody involved in this is dead and that the Crips never received the money, so that he can claim that them killing Tupac had nothing to do with him. But he put a hit out and payed for it.
Chuck Phillips basically already put all of this together in his story for the LA Times back in 2003. His only problem was that his source sensationalized what happened and claimed that Biggie was in Vegas and gave them the gun, when in reality it was Zip.