It seems a bit improbable (though not impossible) that one person happened to go out and "dig up" the over 27,000 pieces that he had in his possession
It might represent a lifetimes work of digging holes or it could be the "stuff" found by other people
Fourteen thousand coins could possibly come from a single find or they might be the product of just a single years worth of harvesting the fields by various small town "syndicates"
I suspect it much more likely that he is a black market dealer in antiquities and probably acquired these things from a variety of people and sources who much prefer to remain anonymous
If he has sources and "clients" (I think it probable) then they are certainly less than thrilled about the prospect of being investigated
He might fear his clients more than he fears the French police !