Luffy probably stops Sanji from marrying Pudding. Sanji is still pissed at his dad and Luffy decides to chase Judge to the Reverie where he and his dad take on the World Government and stuff. Big Mom is pissed at Giants and we can assume all the fights damage Totto Land so she attacks Elbaf. Then Bonney or some other Worst Generation follows her and sinks her ship on the way.
I think Usopp and some of the crew go to Elbaf while Luffy fights Kaido with Law.