LTT uploaded at least a couple of videos explaining how they make money:

https://youtu.be/-zt57TWkTF4 https://youtu.be/Rh5hL47z2us

I think Linus recently mentioned (probably on LAN show) that they are positioned soon to make more money from merchandise than what their YT channel generates - because of their huge drops of the new backpack and screwdriver.

Simply Nailogical did the same thing as did a ton of the beauty vloggers

Christine (host) now sells what appears to be a very successful boutique nail polish line. So successful, she and her SO basically spend more time BSing with their fans (customers) on YT Live and Twitch than making new content

I don't think this is true. I think it's a lot closer to 50/50 for most. Obviously a lot of variability, but YouTube ad revenue is not trivial.

It's not. He's made videos of their revenue breakdown before and from what I remember AdSense still accounts for ~30% of revenue, which is significant.

I own a small career related channel (135k subs) and adsense account for roughly 5-7% of our revenue. The majority of revenue coming from sponsorships. It depends highly on what niche you are in, as some other channels have much higher % accounting for ad revenue