He objectively served zero purpose in the war. I guess he held off King and Queen for some time, I guess that was something worth including him in the arc for, I guess.
I feel like this was such a pointless reason for him to be in wano, especially when Oda went through the trouble of setting up this plot point in zou. If all he was needed for was to stall king and queen, Oda could have just had Usopp shoot them with sea stone cuffs and then have King and Queen chase Usopp around onigashima for 20 chapters. Idk, its not like usopp did anything significant either.
It seems like Oda initially intended for Marco to do something significant, and then just changed his mind. I always thought he would have had Marco use awakening to revive Luffy or something along those lines, but nothing came of it.
I feel like this was such a pointless reason for him to be in wano, especially when Oda went through the trouble of setting up this plot point in zou. If all he was needed for was to stall king and queen, Oda could have just had Usopp shoot them with sea stone cuffs and then have King and Queen chase Usopp around onigashima for 20 chapters. Idk, its not like usopp did anything significant either.
It seems like Oda initially intended for Marco to do something significant, and then just changed his mind. I always thought he would have had Marco use awakening to revive Luffy or something along those lines, but nothing came of it.

