I see some layers to it in my view:

- nostr's lightning bias pushing away users of other cryptocurrencies while the wider Bitcoin bias pushes away dollarbrains, concentrating a certain group of people here

- feeds that boost zapped content

- people who give follows, likes, replies, and reposts to high zap amount npubs, hoping for zaps

- villains who use zaps to promote their own unfair bias willingly

- paid relays and other spam suppression methods that unfairly benefit lightning users or those with more money in general