All might was declared dead to the media after the first battle against AFO since he physically can’t use his quirk despite having it.

This is based on the Bronze Age Superman story where he permanently lost his powers where he overestimated how useful Superman was for the world. Where he always imagined only himself could help, but the world moved along and people learned to trust themselves more as it moved on.

Such as when Clark's as a building more wanting to help, only for the fire apartment and fireman to arrive and saved the people not needing Superman.

I thought of it in a similar scenario, where instead of Superman. It's all might who had OFA, however he's now permanently in a wheelchair despite having his quirk as the world thinks all might died unaware of the super/symbol being dead but not the man.

How would it affect the characters since all might is declared dead years before canon, alongside all might own development if you go the Superman de powered route seeing how he overinflated himself.

That alongside the butterfly effects of no all might for many years, with it affecting Endeavor whose automatically given the number one position after his rivals death and so many heroes, villains, and civilians.