What are some examples in the DBNT category that created unicorn startups? I know lots of DBNT that happened inside of large companies (e.g. Bell Labs). What are some examples of cases where the companies were able to create massive market share from scratch?

Common examples of DBNT were really just DOTB:

Google -> not the first search engine

Apple -> not the first computer/music player/touch phone

Spotify -> not the first music streaming platform

Nvidia -> not the first GPU