User blog comment:NorbertGuitarman/Hisoka X gon/@comment-5780397-20151010174049

1- Ging couldn't have talked to Hisoka, first because Hisoka is a serial killer hwo would be unable to contain himself, second because Hisoka has been looking for Ging to fight him for quite some time.

2- He explains it afterwards, he wanted Killua to heal Gon so that he'd have more opponents to fight.

3- In Greed Island Gon only had a basic knowledge of the advanced techniques, and Hisoka knew he could grow much more, as the Chimera Ant Arc demonstrated.