Sure, and the Bergvall signing was done to ensure Swedish fans keeping coming after Kulu retires, Vuskovic was signed so we'll keep having Croatian fans after Perisic was released, and Gray was signed so we'll keep having English fans after Forster retires.I hate to sound cynical here but Son is likely going to be leaving within a few seasons and he has a sizeable base of dedicated Korean supporters that regularly turn up at the ground to watch him play and that is a LOT of money and a LOT of arses in seats to lose once he leaves.
I don't think Levy is prepared to lose that supporter group and I think that's why this signing has happened.
Now obviously, if he turns out as good as Son did then it's a win regardless but I think the intention behind it is pretty obvious from a business perspective because come rain or shine Korean players in the PL have a sizeable support that will turn up and pay for tickets.