And that was fast because google pushed on megabytes of javascript and tight loops in it. Regular ajax (now known as htmx) webpages worked absolutely fine in other browsers. I regularly scrolled through a whole freebsd single-html handbook and it never lagged in e.g. presto.

Websites aren't expensive to run even on a slow interpreter. Even medium-complexity apps don't do much and could be written in python or ruby back then.

The only source of website lag is ads networks.

Nah, I remember Firefox in 2008 being a miserably bloated and slow experience. Guess it was because of no Electrolysis and any other refinements in the last two decades.

Yep, same. Firefox now is decent, but back in the day it was awful. I remember trying it out early on and immediately going back to IE because Firefox was significantly slower. Chrome was a marked improvement over both IE and Firefox, so it won.