That's probably the same demographic that praises craft beer from brewery businesses, so I think the question should be taken back a step from DIYer to consumer. Here's my interpretation from the US, matching the demo in question.

I'd guess from an economic status, lower income doesn't have the money to spend on craft beer and higher income would transition towards wines. Even though wine and beer can both be made in less than 2 months, beer typically doesn't benefit from aging but wine typically does - meaning better wines incur higher overhead costs for storage for better wines.

From an ethnic standpoint, I don't think I can pin it on anything other than being the majority demographic of the English-speaking world (with your survey/groups possibly being US/Canada focused). Beer is certainly a global phenomenon, but keep in mind your sources will be based by language. However, Germany is the only country I can think of outside of North America where I'd expect diverse craft beer. Maybe their surrounding countries and England too. Everyone makes alcohol, but they may put more resources into wines and spirits instead. Ethnicity likely also ties into financial status on a global scale so once you account for language bias, you'll lose countries that don't have the national spending available for such craft beers.

As for gender, I would put that down as a mix of beer being seen as manly - large quantity of liquid, not sweet, makes burps. Sweet and brightly-colored drinks make many men worried other men might think they're gay (gods forbid you enjoy a tasty drink). So that gives straight men drinking beer and everyone else mixing it up.

Where does that leave us? Straight white middle class men drink craft beer, which spills over into the homebrew English-speaking community demographic.