The pro-audio software market is significantly tilted towards Windows. The split is approximately 75/25. Also, the majority of the "pro"-audio market is not working professionals. In fact, they're a vanishingly small piece of the equation. That's true for pretty much any creative pro-sumer market. Most of the money is in the long tail of people that want to be like pros, not in the tiny number of actual professionals.

Source: I've worked in pro-audio for a long time, both independently and as an employee for one of the largest companies in the space.