IE was far more dominant, and browsers actually had meaningful differences back then. Porting CSS written for IE to Firefox could easily take 50% of the initial implementation time, if not 100%. Today, it's not completely uncommon to have something developed on Chrome working in Firefox and Safari without any changes.
And the most significant problem with IE was obviously that it wasn't FOSS, and was only available for Windows. Neither applies to Chrome.
It doesn't matter if Chrome is open-source, when it is technically owned by a single corporation.
Plenty of web sites aren't for international consumption.
Not at all, as only 20% of the people using mobile browsers at all, are using Safari.
And there was a choice, back then alternatives like Opera, did actually ship their own engine.
