That's the worst part, I don't even know have a guess as to why my brain wanders off. It's just gone and I suddenly realize I haven't been paying attention for 10 minutes. I don't think disgust/escapism can explain it, because it can be an extremely fascinating lecture. But my mind will grab on to a topic and continue on "cruise control" internally before realizing the road has a curve in it. If I had to pick something, it would be related to hyperfocus that just gets triggered off of a random thought.