I believe HN has some automations now that flag posts that look like they were LLM generated. I got caught out by that recently (in a post that wasn't fully LLM generated but quoted a line that probably was.)
(In fairness to this poster, DandyLyons' post was in fact dead when we got here – I used vouch on it.) Probably just weird things that happen when making your first post on HN if it's heuristically not quite right / a Show HN / wordy?
Probably none, just got into HN's spam filter. When you have enough points you can vouche for it and if enough people do it gets reinstated, which is exactly what happened.
You can email the mods and they'll fix it.