You must have missed the line and the reason Anakin and Obi couldn’t go with Ahsoka. They mention the attack on Coruscant and the taking of Palpatine Which is the lead in to ROTS.
Speaking of which, they also mentioned Shaak Ti involved in recovering Palpatine. For those that don’t know, she was originally filmed killed by Grievous on his ship. In the last episode of the Clone Wars shorts (no longer canon even before Disney) that aired before right before the premiere of Revenge of the Sith they showed her perusing Grievous to his ship. Again for those that don’t know, she was also filmed being killed by Anakin at the temple. Later her death was part of The Force Unleased story line which is now non canon. I’m not sure what the official death is as the Star Wars databank does not say anything about her death.