There might be allusions to the Hiroshima/Nagasaki bombing should the Island land over the capital, and just how most post bombing stories involve the survivors picking themselves back up, Momo will rally the people that Wano can be rebuilt as long as it has people.
hmmm
I already think the explosion should occur at least as fake hype fir act 3 end.
Like this onigashima explode in air above the capital act 3 end,
act 4 we see onigashima destroyed to parts and kaidou flames are gone , the capital people are running away from the falling rubbles.
Momonosuke save citizens by making some rubbles float , also otger members of SHs and samurai are saving citizens.
onigashima side almost everyone is ok but they already fallen in the capital
thanks to zoro he cut the explosion before it destroy everyone.