It's not just the branching factor. It's also the fact that the quality of moves in games like chess can be evaluated relatively quickly, say, within 10-20 turn

It's not just the branching factor. It's also the fact that the quality of moves in games like chess can be evaluated relatively quickly, say, within 10-20 turns. In Go, on the other hand, a stone placed at the beginning of the game may be critically important 100 turns later.