Why does meditating cause me to lucid dream?

I’m trying to meditate for the first time while listening to a meditation tape and slipped into what I could only explain as a lucid dream. It was like a dream, I couldn’t get out of it but could control what I was doing in the dream.

 I didn’t remember until now that this happened 10 years ago while listening to meditation tapes for sleep. I was working night shift and couldn’t sleep during the day, a co worker gave me a cd for sleep hypnosis and after listening to it a few times, every time I tried to fall asleep I would fall into the most realistic dreams that would start from where I was sleeping and Icould control but turn really scary.