I think that we choose a path that is most convenient for us (or at least we think so).
Thus, even when people DO believe with conviction in ghosts and black magic, it is easy for them to deluded themselves about it by surrounding themselves with people that either choose not to care (recklessly-defiantly) or simply do not believe.
Then enters into motion a very basic human behavior: IF I AM NOT ALONE I'LL BE FINE.
Humans can engage in all sorts of TERRIBLE things that THEY KNOW are WRONG, but because they are in a "GROUP", they just go along with it as if a warning light got dis-engaged...
Examples: deporting Jews to death camps during World War 2, taking part of a gang-raping, abusing and killing animals for food even!
WE would be able to do anything and mold anything if we are surrounded by people that make us feel protected if we adopt the general thinking, if we make ourselves fit the mold.
We feel protected because:
1. we are not exposed,
2. we are not alone,
3. we don’t have to put on a thinking cap.
If the great majority around us believe that ghosts do not exist, that money is a solution, that having families and children is a solution, if getting drunk or high is a solution or even that sacrificing animals or even human beings is a solution, we would surely fit in unless we apply analytic logic and courage to drive our actions.
Everybody believes in ghosts, I have that conviction, simply because everyone has been a ghost and knows it to be true first-hand.