It means someone that is interested in women and may also imply that this person is also good with women

We need more clues. My guess is that the phrase is being used sarcastically. The "because" is an indicator that the person being spoken to isn't about "the ladies" at all. But without context, it is difficult to tell.

This phrase means someone puts a lot of focus and attention toward women or toward obtaining women. If a man is always pursuing women, if he exercises and changes his appearance with the aim of getting women, and he flirts often with women, we might say he is "all about the ladies." Men/Women who are very interested and make choices based on the pursuit of getting women, we'd say they are "all about the ladies."