Color me shocked.
The military isn’t a monolithic bloc of conservative voters. Lots of troops aren’t political at all. But there is a decided conservative slant to the culture.
Having said that, you’d THINK the military would be an almost ideal recruiting ground for liberals. It is full of young, idealistic people who are motivated enough to take action to achieve their goals. It has long been the most minority-friendly employer out there, where people can rise based on competence and effort, not political connections.