What logic? The person you’re replying to didn’t explain their reasoning, so any logic you’re seeing is being constructed in your own head and projected onto someone else. In other words, you’re likely responding to an argument you’ve seen (and disagreed with) before instead of what that poster had in mind (which may or may not jive with what is in your head).
Google doesn’t just show ads, they track you and have the infrastructure to sell your information to people who buy ad space. That is fundamentally different from a website that makes money by showing ads, many of which they don’t pick themselves. So yes, Google is an ad company. And they’re one “first” because that’s where their efforts are, not because of the revenue. YouTube, Chrome, their web proposals, it all serves the same goal: ads, ads, ads, and keeping Google’s dominance in the space.