In the Election arc, Ging confidently tells Pariston Gon won't die. How would he know this? Sure he has trust in Gon's friends, but Gon's condition was like nothing ever seen before, even if he has good friends it doesn't mean they can help heal him. I'm not sure why Ging would be so confident in something so baseless.
Well it is
The more powerful/nen expert a person gets the more
intuitive he gets. Experience also counts as one factor.
If you remember the time during GON returning to
whale island after
hunter exam with killua, he received
greed island contents from
mito which was given by
1. How did Ging know that Gon would attend Hunter exam ? 2. How did he know if Gon would qualify underground exam and learn nen ? 3. How would he know how the Zodiacs would react in President election(after netero's death).
This shows how experienced and intuitive he is. As said by
netero regards Ging as one of the 5 best nen users in the world.
Similarly, Ging knew Gon would not die.
This might be the explanation for your question!!