From the article: an 8 year old kid, Stroud, wrote a book about Minecraft.

okay.

Question is now: is it because of Minecraft that this kid "became a writer", or was it just the starting element? If the kid had been fond of frogs, rocks or knitting, would he gave wrote a book just as well?

If you take any random kid playing Minecraft, could you turn it into a writer like described in the article?

I think that the kid was a born writer, or is in the correct environment, but crediting Minecraft for this is not correct.