Chelsea is about to sell Havertz, Kovacic and Mount. They really don't need to sell Ziyech, Koulibaly or CHO to balance the books. Ziyech was of interest in January for a loan move and I'm sure he could've been sold or loaned out in Europe if needed, Koulibaly has a lot of interest back in Italy so could have been loaned back there if needed. CHO hasn't been good in some time but I'm sure they could've found another loan home for him if they wanted.
Is the Saudis buying guys Chelsea wants to move on convienent or coincidence? I would learn towards not a coincidence because I highly doubt Chelsea bought Koulibaly knowing they can dump him in a year and messed up Ziyech loan because they knew they could sell him instead. Arsenal selling a useful player with off field issues is more a conspiracy to me than what Chelsea has going on.