Once you have been in email contact with someone who subsequently joins a “social network” — that “social network” raids their email for any addresses it can find, and invites you to join “Joe Bloggs” on that social network.
If anyone of them is silly enough to join that “social network” in order to opt out — then that “social network first raids their email addresses, and the process is repeated.
It’s like a virus.
This is why most of us here refuse to have anything to do with “Facefudge”
Just keep them all going to spam (but check for genuine emails) and it should all start to trail off over the coming months. Unless that person joins another “social network” (like Google’s own) ………