I think oda planned it well. Making Onighisima float above Flower Capital exactly at the time People are sending off their fire Lanterns. It will just illuminate the whole sky, and they can witness everything In the dark sky at the moment.
Imagine Luffy or zoro ( Whoever Takes down kaido) taking down kaido while kaido being In the sky Being in the fire mode. Being illuminated himself , Everyone can easily see that now.
People wishes of living happily and Getting rid of kaido, Both things at the same time. Last time luffy defeated a main Arc villain last time was Dressrosa where everyone was praying/Running around/ in chaos. Because of doflamingo , And luffy took him down while everyone witnessed that and people wishes getting accepted and getting their actual ruler back.
Similarly , Luffy/zoro defeats kaido infront of everyone, In the illuminated sky , A double spread of beautiful panel with full moon with kaido passing out. While momonuske actually using the lanterns Flames. (I THINK DRAGONS HAVE THE ABILITY TO CONTROL FLAMES). SAVING everyone by making the lantern go the way he wants. And hence getting their People trust back with saving and killing kaido.
Kaido has settled up for so long , Fire festival was Declared in the series chapters back , and now it's coming into the play.
Or even kaiddo could end up Taking lanterns as his own power up, For the final attack. Which makes kaido Fire dragon mode even bigger, Flying across the fire capital witnessed by everyone.
Lantern either will help Momonuske or kaido. But whoever it helps it will be witnessed by wano People. And so far People haven't seen a thing due to clouds and dark sky. This just the absolute perfect ending Of Wano Final fight. I dint expect more 4 chapters. For this.