each time you state you don’t think in fairies one passes away.
So perhaps they have actually all died off already?Seriously, though-
the power of recommendation has actually been well recorded. I’m not aware of any clinical studies that reveal that voodoo or black or white magic work, however “science” is naturally searching for experiments that can be replicated, and it might be that sometimes these things work, and at other times they don’t, for factors not yet comprehended. The OP’s friend might be a victim of some nefarious deed, but it would be essential to dismiss the numerous other possible reasons for his behavioural modification, change in diet, change in medications, slow poisoning by the wife/gf, and so on, alter in financial circumstances, etc.