Sometimes players will bust.
It is what it is. I always saw Pulju as someone that had a high chance of busting in NHL. He was not a guy that was NHL ready, just a guy with a lot of raw, unpolished talent. That's why Kekäläinen picked Dubois instead, knowing he'd get more immediate results with less micro-management.
The past few years of his development have been a total waste, so at this point I can't really see a projection for him as a NHL player. He was probably better coming in, than he is now. He will be a solid guy though, at Liiga/world championship-level, once he gets to play in a comfortable environment.