Well, first of all, we know Dylan was not a social butterfly as extroverts tend to be. Instead, he was hypersensitive and intensely over aware of himself. Extroverts are often naturally open and curious with other people and more importantly, are unaware of themselves while being in the company of others. They feel energized being around people often. Whereas introverts need to be alone for periods of time in order to recharge their batteries.
As for Dylan’s ability to act in the video productions: often the shyest people shine in front of the cameras because they are happily able to be someone other than themselves. It’s a known thing that excellent actors are often shy people in real life. They give an impeccable performance and can seem to transform themselves into appearing like extroverts for various roles.
“Dylan was the sweetest, cutest kid you’d ever meet,” said Brooks’s father,
Randy. “He was really shy, though, and it would take him fifteen or twenty minutes to warm up to us every time he came over, even though we knew him and we were close to him. After he’d warmed up, he was okay.”
Judy Brown remembers Dylan Klebold as “a sensitive, caring child” who
worried a lot about what other people thought—perhaps too much for his own
good. She recognized the way that Dylan seemed to internalize what was bothering him, rather than being open about it. It was a familiar problem
Even around people he knew well while being in the company of friends and close family, it could take Dylan a good while to relax enough to be himself around them as it did on his sixteenth birthday.
During the Frankenstein Roast video, Brooks stated it took Dylan a while of being quiet and observant before he was able to actually start participating in the roast exchanging jovial barbs with Brooks and Zack. The entire time he was awkward – nervously, repetitively, tucking his hair behind his ears.
Devon mentioned that “he didn’t know how to interact with people without another person there or something that he could talk about like a movie or music, or something.”
And Dylan himself knew full well of his social anxiety, his ‘shyness’ around people:
“me looking weird & acting shy — BIG problem, me getting bad grades, having no ambition of life, that’s the big shit. Anyway ...”
or
”I hoped we could have been together … you seem a bit like me. Pensive, quiet, an observer, not wanting what is offered here (school, life, etc.) you almost seem lonely, like me.”
My personal feeling is that Dylan’s acute, pervasive “shyness” which he had since childhood began to evolve into AvPD especially because of his marked feelings of inadequacy and sensitivity of negative criticism and rejection. I discussed the case for it in this post.

