But I can probably answer why Snowflake instead of Redshift (sorry, not too familiar with BigQuery)...
First of all it's cloud-provider agnostic so you can set up Snowflake on any or all of the 3 major cloud providers as well as set up replication between them directly or indirectly through their data exchange. Probably the most powerful feature is the way that Snowflake has the ability to scale (up or down) compute (vertically and horizontal) and storage independently of each other. Furthermore, you have the ability to scale compute down to nothing, and spin up "instantly" when the demand arrives. On top of all of this there is an incredible selection of functionality that i could go on and on about.
Edit: seems you’ve already answered this :) https://news.ycombinator.com/item?id=24265856
Marketing. Vast amounts of marketing.
Edit: why are so many people downvoting this? Is there some other reason for Snowflake's valuation (aside from tech bubble playing a role)?
W/r/t value, the idea is a disproportionate of egress from Oracle, Teradata, etc will end up at Snowflake, hence huge TAM, SAM, and SOM.
> This still in no way answers why Snowflake is so valuable, though.
It explains it to a T! You have something you want, but internal company politics and territoriality keep you from getting it the way you want. An outside provider lets everyone get it for a bit of cash. It's basically the same play as Salesforce. It's not some kind of technical moonshot. It has to do with a modicum of technology delivered by a 3rd party who can avoid all of the internal friction.
The next founder who can think of this kind of play, then execute on it, will be the next Salesforce/Snowflake, and will probably have the ear of the same investors!