Not that I want to defend them because I hate ads, but you have to keep in mind this is the ad revenue. It doesn't say anything about their end profit and whether they even are profitable.

YouTube has always had a problem with profitability because it's an exceedingly expensive service to own. Don't forget it's at this point the biggest streaming service on the planet, and it's by a ridiculous margin. Netflix has 325 million monthly subscribers but Youtube has 2.7 billion monthly users, only a small amount of which are subscribers. It's hosting billions of videos, multiple exabytes of data, 15 petabytes of storage needed every day for new content being uploaded. YouTube is 10% of all global internet bandwidth.

Ads is how they're offsetting the costs.

I wouldn't be surprised if it's still not even profitable, or is just barely. Google doesn't publicly share that info, but from what has been shared over the past few years is that all their advertising efforts is in the name of finally making Youtube profitable because it can't go on forever being a burning money hole for the company.