He seems nervous around me, why?

I used to have a crush on this guy, about seven years ago. Now when I'm near him he seems really nervous. He's super friendly to my dad, and makes a point to give him a big, happy hello. He talks super fast when I'm around, laughs, and one time he was making a note and was typing at jittery lightening fast speed. One day I was about to pass him on the sidewalk, he didn't know what to do and which direction to go. I have zero interest in him, I just wanna know what you think.
He seems nervous around me, why?
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