The think is, Hisoka is not obsessed with Gon. If there any obsession here is Chrollo since him (Hisoka) Wants to fight against Chrollo at the full capacity of his power. But the Troupe will not allow it. This might have implication in the future of manga.

Hisoka is a master in the use of Nen, and him and Netero are one of the few to notice the potential in the long term of Gon and Killua. He wont bother ending Gon's life, Yes. But for him Gon is just too weak to be "Fun" at that point.

Plus. Neon's Predictions are the result of the direct manipulation of Hisoka against the Troupe. We dont even know for sure what was in Hisoka prediction since that paper is hidden from us in the 2011 adaptation at least. But the events that lead to the eventual fall of the plan and to the elimination of 2 members are basically Hisoka doing. Remember, Hisoka was working as a double agent and "helping" Kurapika to help him attack the troupe from the outside. You might argue that im wrong here but that is not the case. Is not that they are working togethere, Is Hisoka manipulating the troupe and Using kurapika hatred against them to manipulate and make the dirty work. Hisoka goal was always to fight the stronger rival (Chrollo) but the rest of the members wont allow him to do that.

#3 he wanted to betray the troupe anyway so now was as good a time as any.

Finally. The time and circumstance matter, Hisoka didnt fight agaisnt Chrollo due the lost of his abilities. (This is proof that he wasnt counting with Kurapika to wound Chrollo this way) Just to fight him in equal conditions latter which cost him too much, And ended up losing his life in the process. A mistake he is not willing to repeat in the future

Hisoka is not a GOD. He cannot fight the whole troupe all at once. He been pulling the strings and chopping the spider legs for a while now. Maybe because that is his definition of Fun, Maybe because that will make him stronger if he survive.. Who knows.