
was it ever explained why the red dragon was the only one who reincarnated as a woman?

Because she's the only reincarnation? The others aren't reincarnations of the previous dragons or anything. They're dragon warriors, who just always happen to be born in the same tribes. But there's no soul being repeated, those are fully separate people.
In this case, she is a reincarnation of the first king, who was the crimson dragon encarnate. Souls don't choose the bodies they land in, they just are.

The villains (so far) have been repetitive 1 dimensional psychos they feel less like characters and more like obstacles the main couple are supposed to overcome hopefully the next arc has something different or at least has villains that are more complex (tho i doubt this will happen as the author only seems to know how to write villains who are crazy)

y'all are some weirdos calling mc a bl bottom
not everything revolves around bl
further proof bl gives you brainrot

I mean... if you see something so common that you don't normally see in other places, of course, you are going to point it out. It doesn't mean it makes them weird lol. Observation is not always how you view them... However, you are right about some commenters... Applying what they see in other manhwas in to some place where it doesn't belong... Ehh..
the shy informant is so cute