So ... short version of history:
Seattle was not originally 'Seattle'.
It was a bunch of different smaller towns, all nearby each other, that grew outward toward each other.
As a result, there were many differently oriented street grid layouts... that roughly all smashed into each other at downtown/pioneer square.
The... the meeting where multiple proponents of different street grids, basically mayors of the smaller but now merging towns... where they were supposed to agree on how to make a unified system?
Literally devolved into a a brawl, a melee.
... That's why Seattle's street layout fundamentally makes no sense.
That and the pretty extreme terrain. Try walking all the way up Pike or Pine, from Pike Place Market, all the way up to Capitol Hill.
Steep grades, lots of hills.
Check out the Seattle Underground tour if you want a more comprehensive explanation of this batshittery, lol.

