Historically, the idea that a freer market and capitalism go hand in hand with democracy does have some merit. The fact that business became a more important factor for the power calculus meant that it was possible to challenge the autocratic status quo, and democracy was an alternative that was naturally favoured by many businesspeople at first because it promised a more meritocratic system.

Nowadays, the super rich have more power in practice than many of the autocrats who were thrown out by democratic movements of the long forgotten past, so their hubris leads some of them to work towards establishing autocratic structures again, believing that those will always work in their favour (newsflash: they don't, but that's another topic). Since capitalism alone does not put a check on this development, it is no longer a good ally of democracy. Still a useful tool when applied with measure and combined with other tools, but not an ally.