There was a time back in the IE6 era where firefox didn't really have any market share and adblockers weren't really a thing.

The advertising industry was really aggressive even then. Some publishers put as many popups and banner ads as they could. I'm not saying all publishers would do this, but I have to admit the worst actors are the ones I strongly remember.

Only difference now is that there's a lot more tracking and ads are more insidious where they blend in with content now.