Revenue

Unfortunately, revenue and profit are not synonyms. Revenue is money made before taxes and expenses. Yes, their revenue has increased because their userbase has increased. Users who are served advertisements. If users block advertisements, revenue decreases* while expenses increase due to more traffic and data storage required, reducing profit. Since YouTube doesn't flop their dick out on the table often, we don't know exact numbers for expenses but in 2015 when they did whip it out, it was at a loss. In your own link, the only methods it cites for Youtube 'profiting' are advertisements and premium. A userbase is only valuable if you can advertise to them, sell their data, or get them to pay a subscription.

• Revenue technically doesn't "decrease" in this instance but just fails to "increase" because advertisements aren't being served to users that otherwise would receive them.

If enough people block ads, it widens the margin between cost and revenue which can lead to "negative profits" or a loss.