He could not do before? He did this while he was alive, it's been explained how he used the properties of his Bungee Gum to make it work. He was surprised that his Nen activated after death. That's all.
Camilla's ability is empowered by her death, she says it herself.Since she is dead and her ability makes her Nen active in that state, it's stronger as long as she is not resurrected.
This is down to interpretation imo until Togashi really explains it... But personally I do think that Hisoka received some sort of boost to his Nen after his death. He immediately showed new techniques which would of benefitted him during the fight with Chrollo, and so leads me to believe he was only capable of these things after he revived himself. Such as the recreation of the hand and foot he lost. Using his Nen to ''wrap" Machi up like that was a far higher level of emission we have seen from Hisoka as of yet, normally when he uses an ability like that he has to maintain some sort of connection to the Aura like the thread on Gon's face, this opens up ALOT of new possibilities. The way he used the new foot as a spring was also new, and the way he took out Shalnark in one swift blow like that it almost seemed like he received an overall boost in strength.
It's not a new concept by any means, and I've always thought it's related to someone's will and desire to do or achieve something before they die. Both examples we had actually seen of this happening (Pitou and Hisoka) they had a major goal or desire they had to fulfill, Pitou in killing Gon to protect Meruem, and Hisoka's desire to defeat Chrollo and in a broader sense just strong self preservation, also a big difference in Hisoka's case is he actually specifically attempted to do it, which might be a reason for the strength increase.
Camilla seems to of based her whole Hatsu around this idea, made easier by the fact that she is a specialist. It's more then possible that the Cat becomes stronger each time it's used. I also wonder whether the Cat is restricted to attacking the person who killed Camilla, and what happens if the Cat's first attack fails, does it continue to stay around and attack the person who killed her until it can absorb them? Or can it use anyone nearby to ressurect her?
I have a theory that Chrollo also understands this concept alot more then he gave away during the fight with Hisoka, he didn't really explain how he came to know the elder from Meteor that he took Sun and Moon from.. Chrollo's ability requires him to either force the person to fulfill the requirements or he has to actually coerce the person into giving him the info he needs, meaning he would have to actually know this person fairly well, be close to them or at the very least have a conversation with them.
He also didn't tell us how this person died or why they died, or what his connection to them was. We know that for the most part, the abilities in the Bandits Secret are stolen either by tricking people or forcing them to give away, and that they dissapear from the book after the person's death, and we can assume that for all of these abilities Chrollo holds no attachment to the people that owned the abilities originally, like he would for someone like Shalnark for example, or Kortopi.. See where I'm going with this?
I think that if somebody WILLINGLY gives Chrollo their ability and then dies, he retains the ability after they die AND the ability becomes stronger. This is why Sun and Moon didn't dissapear from the book, and also why Togashi included the lines between Chrollo and Shalnark in which he offers to give him Black Voice back but Shalnark DECLINED. It was that particular scene that gave me this whole idea, why would Togashi include that if Shalnark were to die and the ability dissapear anyway? It would be a completely pointless line. This means that ANY member of the Phantom Troupe could give Chrollo their hatsu to use FOREVER before they die.
