This video is purposely being kept off the front page. Number 8 has 7 points, 1 hour ago. This has 20 points for the same time frame and is now 40 and dropping.
I would think that people flagging the story is weighing it down. If the talk is good, why would it be flagged? Maybe because the title of the submission is kind of sensationalistic relative to the talk. The talk is about working more on solving important problems, less on making cat picture sharing easy and fun, and it's not so much about him leaving his job, though it does illustrate his intentions.
It would have to have been a huge number of flag votes -- too many to be a reasonable explanatoin. My guess is that it was moderated down. Which leaves the big question of why?
Is it because the YC portfolio is heavy on cat picture startups and light on startups that do something important?
It may be that managers don't want their employees seeing this and being inspired to quit to work on more meaningful stuff -- it would be like a run on the banks in the tech world.
Clearly, said employees need a video of Steve Yegge saying this in 2011 to realize they're working on meaningless stuff. xkcd #137 five years ago came close to marking the point, but it took Steve on Youtube to really drive it home.