> KHTML had almost no market share - it only ran on KDE, and most KDE users used Firefox.

As mentioned before, Firefox didn't even exist at this point. And KHTML itself actually predates Linux Gecko by a few months as well.

Don Melton forked KHTML/KJS internally in 2001, and announced the work to KDE at the beginning of 2003... GMail wasn't released until 2004!