Every node has a different view of the network based on the gossip it receives. nostr:npub19tcpurtt6xulhw0r6sc404j9jraj0h8me2lzs7z2tqewz7l0hpas59nlea uses several nodes to feed its database, which contributes to it seeing the highest amount of nodes.

Https://Amboss.space/stats shows the comparison over time.