My guess, from having worked on statewide campaigns and following politics for my entire adult life (which is to say, I have no fucking clue but am happy to posit my opinion): his campaign knows their base includes a lot of young tech-savvy folks, and their tech team (who is well aware of this fact) wrote a quick script for him to spend a few minutes reading in front of a camera one day when he was at HQ. I would imagine the entire point was to generate exactly this discussion on exactly this (and a handful of other similar) website(s).