Many of these https://en.wikipedia.org/wiki/List_of_unicorn_startup_compan... could've been in theory done (to the point that there was no room for a multi-$b startup) by Google (Canva, Instacart, Telegram, Miro, Airtable), but weren't.
Also a billion $ unicorn is not the same as billion $ revenue.
[1] https://wolfstreet.com/2023/04/26/what-are-we-going-to-do-wi...