I'd bet that it started out as feuding clans but Yamamoto allied with the laid back shiba, kicked so much ass on his own that having the shiba on his side united other clans and eventually he got the loyalty of the clans that bow to the strongest.
The only ones left were the prim and proper...
The way I see it is that it's something like the christian heaven.
Everyone gets the paradise they want, the limited tsukiyomi changed things and made them a shared experience for sakura and naruto but in the full tsukiyomi they'd get their own heaven.
I'd have more respect for Naruto if he had a sane plan for peace...like getting all of the people who control the elements to manipulate farmland and the earth so there's a mountain sized skyscraper where everyone can have a large home, all the food they can eat and using ninja arts to end...
My theory: The only reason Ichigo has a zanpakuto in the first place was because of rukia.
Without a zanpakuto he would've been a quincy elite.
His zanpakutos final form is a black cero because of his hollow side.
Ichigos final form will be a mix of everything, Quininihollowgamibringer