Bluesky is smaller than Mastodon.social _alone_

Mastodon.social and Mastodon.online host about 400k active users with a handful of moderators and developers funded on a $30k/month Patreon, plus whatever the project gets from Liberapay and the thing on Join Mastodon

What is Bluesky doing that it needs so much money for, that's worth giving up a piece of the company to investors?