Except, he literally said he will leave after getting "Strawhat Luffy". His intention wasn't to "moniter the war" lol. He had zero interest in Wano beyond that.
Ryokugyu, to fodder Marines: "Don't tell Sakazuki what I'm upto."
He was never sent to capture Luffy, but rather something he wanted to do off his own volition to get a good name in Akainu's books.
Like i said here ->
Ryokugyu just additionally went ahead, negged the two YCs and tried to bring Luffy's head back to Akainu to surprise him.
Gaban is not currently planning a trip to Wano, nor has he actually gone to Wano, even though Kaido is dead. Kaido was not keeping him from going to Wano, he simply is retired and wants to visit the country again sometime. Unless Gaban caused trouble, Kaido would not try to kill him, the SH were undercover in Wano for a good amount of time.
His words tell you all you need to know, feeling happy that now he could go back to Wano again after talking about how Luffy took care of Kaido.