The official info we have:

"Why are updates taking so long?

Due to the large number of players at Valheim's release we had to prioritize bug fixing, balance and optimization issues. This meant that we couldn't put all of our energy into Hearth & Home until later than expected, you can read more about that here. In general, updates take a long time because we want them to be good and polished before we share them!"
(from the pinned FAQ thread)

They are now a team of 13, I think by the time of the Steam Early Access launch, they already were 5. I think they said they want to keep the studio small.

From what one of the devs commented here a while back, most of the team are regular employees, e.g. they are not chilling in their supercars. A huge part of the money left after taxes, publisher, and Steam is apparently in the bank to make sure they can support their studio for a good long while.

Feel free to correct me, or add to that. These are my personal recollections, not a statement from IG.