As this was a public referendum, a supermajority was required to have it pass. For details, see #adaptive-quorum-biasing" target="_blank" rel="nofollow noopener">wiki.polkadot.network/docs/learn-gov…
Referendum 118, proposing to gradually increase the ideal number of validators in the active set on Polkadot to 400, is now failing with 33.6% in favor. polkadot.polkassembly.io/referendum/118