It's well known that to get to the front page you have to submit then get two dozen friends (with good rep) to upvote you within a short period of time.
Since the moderation log is hidden I can only guess what happened. But last year we got the confirmation of the removal via email and the explanation was that the post wasn't "that interesting". https://twitter.com/chadwhitacre_/status/1716947994338021885
I expected this again and thus kept monitoring the index page actively. The post stayed on there for quite a while and suddenly dropped off to the second page and then a while later completely.
Crazy I missed that. That certainly damages the trust I have in this site - it already benefits YC to have this community, they don't need to play favorites.
It feels like we're being treated as a sales funnel when they pull tricks like that.