Jujutsu Kaisen left a lot of questions unanswered with its finale and almost everything regarding ... one body to another through his brain but that is almost impossible to discover at first ...

The first possibility is that Kenjaku had to work some way to attain all of Geto's memories. Perhaps, the control that he had over the body swapping technique was much greater than that of Yuta ...

For the very first time In a very long time ... once Gojo started speaking to him after finding out about Kenjaku taking over ...