Firewalking is based on the scientific fact that coal ash is a very poor conductor of heat energy, that is, a good thermal insulator.
So its nothing mystical.
[skepdic.com]

In theory you could say its a type of "dare" to do something you are irrationally afraid of, so it'll give you a "high".

But of course, its abused to manipulate people in these LGATS.
More Hype.

Coz