In the most recent chapter, Marco the Phonix has appeared in Wano in order to assist Luffy’s Alliance in the Battle against Kaido and Big Mom.
But in chapter 909, Marco stated that he would not be able to help the Straw Hats, as he had to guard Whitebeard’s home village in the likely event that Edward Weevil tried to attack in order to find Whitebeard’s fabled treasure.
In order for Marco to come to Wano, the threat of Edward Weevil would have to be removed.
In chapter 956, it was revealed that the Shichibukai system was abolished during the Levely, with the Marines Special Scientific Group(SSG) has been established in order to replace them.
As a result, the Marines have begun simultaneous operations to capture all of the Shichibukai, including Edward Weevil.
I believe that the Marines deployed whatever the SSG created in order to capture the Shichibukai and that they managed to capture Edward Weevil, along with probably at least a couple of other members of the Shichibukai.
With Edward Weevil in custody, Marco would not have to worry about Weevil coming to attack Whitebeard’s home village, allowing him to go and assist the Straw Hats.
*Theory by strongerthenbefore20