Severance

Remember the "Allentown" glass cube with Marks head, which he got for his "freshman fluke"? And later we saw that it's the room where Gemma is forced to write "thank you" cards, which Mark knows she hates? He completed his first file very quickly due to his connection with Gemma, and he's presumably the only one working on her files. We know she has 25 rooms, and Mark has completed 25 files. His outies' connection with & knowledge about Gemma are being used to speed up the refining process.

As for why nobody else was working on her files, it's something I hope we learn about in season 3. My current theory is that Gemmas personalities are supposed to come pre-loaded onto the Severance chips, so essentially they're condemning her innies to an infinitely-copied hell in other peoples bodies. But Lumon can hold people only for so long before they find a way to end themselves. Once they found that the personal connection between Mark and Gemma allowed him to quickly go through her files, all the focus was on getting all the 25 personalities finished ASAP. The other refiners were probably just preparing the chips for new severed workers.