Nostr Trend works based on interaction and the relays you are connected to. Sometimes you might have a post with many zaps, but it only appears in the "Most-Zapped" category. You also need to be consistent; keep using the hashtag, and it tends to become popular because the project is quite interesting. One of the posts that stayed in the trending section for a long time was by Jack.

nostr:note1dvf5kk8mhnnnmptrqffx9yqx5d46ywwcgwl2vwg4tvvga8rl2nfqkzkfaf