This was a great writeup. I went back to Spotify to try out Discover Weekly around this time last year, and it was absolutely worth it — although it has a bug which means it will slowly but surely fill up with songs it’s recommended earlier that you didn’t like.
I have heard that the people who make Spotify’s manually curated playlists, still rely a lot on automatic discovery algorithms to find candidates to add to these lists. And although online talk is a factor in these algorithms as you say, the algorithm actually does analyse the sound itself. So maybe you weren’t just lucky with early online attention — maybe your music was actually just that good! How that’s for inspiration?
I don’t think anyone added you manually to the Discover Weekly pool. Looking at the tracks I’ve been recommended over the last year, none have below 10000 plays, so I think that’s the only limit. Probably you got over that limit by being featured on Fresh Finds. Release Radar and Daily Music Mix don’t even have that limit.
Good luck with your further career!