And Go itself is some years old now (created in either 2007 or 2009 - according to its Wikipedia article - maybe they mean initial creation and first release for public use, by those two year values). So Go is about either 8 or 10 years old. And that makes D either 16 or 18 years old.

>Go had a lot of success breaking into the Python market, why couldn't D have instead if they had put their efforts there from the beginning?

So when D was new or just a few years old (13 to 16 years ago, say), the Python market was a lot smaller that it is today or has been for the last few years. It might not have even been a target for them, for that or any other reason - another reason could be that Walter is from a systems and compiler background, so might not have been too interested in the domain of interpreted languages (just guessing here, maybe he will comment on this). But BTW, D can be used almost like a scripting language due to its speed of compilation. See rdmd command and the "Why D?" and "D as a scripting language" articles on the Infognition blog (a google away).