I think Bitwarden uses Lunr for search, so probably their relevance scoring algorithm: Searching : Lunr
This causes multiple occurrences of match to rank higher and other behaviors.
Certain matches are also boosted in score jslib/search.service.ts at master · bitwarden/jslib · GitHub like match inside first 8 characters (shortid).
There is also a feature request to tweak the boosts Improve ordering search results with several words by relevancy