As usual in such cases, some of the delay is my incorrect choices, and risks that didn't work out. But most of it is things I could never control or predict. The only thing I could really have done was not to crowdfund this book in the first place.
A lot of people are understanding, and a lot of others just don't care much (which is fine). And then there's always some people who will give you hell for not meeting expectations, and I don't have enough thick skin for that.