I don't really have any evidence (hopefully Google will be required to release that evidence in a monopoly probe) besides what I recall from advertising but sec

I don't really have any evidence (hopefully Google will be required to release that evidence in a monopoly probe) besides what I recall from advertising but security certainly doesn't seem to be the primary factor. Speed certainly brought in a lot of users, but by the time Firefox caught up, I am not sure what the market share was (at first there was a huge difference in performance, I don't think that today's difference in performance is comparable).