In light of DeepMind's recent victories and loss to Lee Sedol, what is the history of "Go" and why has it taken so long for computers to become as good at it as humans compared to chess?

Go (aka Baduk or Weichi) underwent a rennaisance in 18/19 century Japan. They developed the ranking system and new strategies. High level competitions became popular events. In the early 20th century there was more radical change, especially in the opening gambits (fuseki). The Japanese developments spread to its neighbors. I
think current international competition is purely post-war, with China and Korea matching and surpassing the Japanese.
Yes, there are many cultural references, such as the Novel 'Master of Go' by Kawabata. The Go ranking system (kyu-dan) was borrowed by Judo and is now common through martial arts and other activities.
Completely unrelated - Go is a game of enclosing territory. I have a personal theory that the Viking game 'Kings Table' is based on traded go sets.
The military leader poring over the go board is a standard trope in fiction. In real life, Mao Zedong is theorised to have used a go srategy (The protracted Game - Scott Boorman).
No idea : )