My guess is straight from the club.
There was a Panorama or Dispatches documentary on earlier this decade showing record companies doing it for gigs.
It’s not fans who’ve already got a ticket who re-sell tickets on the tout sites, it’s the record companies.
They hold back a fair chunk of tickets for gigs, only allow a certain amount to be sold the real way and then post the rest on the tout sites to make a fortune on them.
There’s no way football clubs aren’t doing the same thing. They are proper money grabbing bastards modern football clubs.