Dreams of my ex from 10 years ago

I’ve been no contact with my ex for nearly 10 years now, she’s moved forward in life and is married living in another state. Since dating her I’ve been in 3 different relationships and have been happily dating my current girlfriend for 2+ years. Lately almost every single night I’ve been having extremely vivid dreams about my ex and really wonder why. Our breakup was one sided and hit me very hard, and tbh I don’t think I’ll ever be truly over her, but why am I having these dreams now after almost a decade?