At least with Japanese, the answer to "why it took so long" is "nobody really cared".
Vertical writing is only commonly seen in books and very formal documents these days, and word processing software to make them have long supported it. Most writing, by hand or by computer, is done horizontally.
Vertical writing is only commonly seen in books and very formal documents these days, and word processing software to make them have long supported it. Most writing, by hand or by computer, is done horizontally.