This isn’t a recent thing. I’m no expert in this field but my understanding is that most of the old masters had a “studio” full of assistants and apprentices who were largely responsible for the work attributed to the artist.
Just a few days ago I was looking at a Canaletto that was really pretty rubbish. Apparently he never visited the scene of the painting - his assistants traveled, came back with sketches etc and he finished it off, apparently in a rush.