Ok, here we go.
So The Big Three, as seen in the title, have been on a very long vacation after the last Switch War and after hearing the reports of violence, anarchy, and general chaos, they decided to make a comeback.
The former Alliance of the SIth has gone it's seperate ways. Darth Vader is currently leading humanitarian efforts in splatland, and Palpatine and Grevious are just chilling out on the Death Star.