I understand that kidnaps are not to a particular set of people or a particular geo-territory but that of a specific and significant person as the co-founder of Ledger is of immense concern.

Looking at it from different lenses will further explain the worries assigned to it. For reasons of the importance of what Ledger stands for in the crypto space, the possibility of divulging classified information in exchange for his life, the possibility of compromising the finances of Ledger's customers are far more dire than considerations bothered around family ties as possible causes and personal rifts with friends, etc.

France isn't a city that has a porous security framework and kidnapping of high-profiled individuals on its soil is rare, this gives the crypto space something to look at in terms of the exact cause of the kidnap.