I use FF but Chrome is objectively better in side by side comparison. It's faster, more web pages load correctly, its UX is much nicer. For most people, you just install it and go. Most people don't have the time or inclination to faff on with a browser, much less for something as poorly understood as privacy. It has features Firefox doesn't, such as tab groups which Mozilla stupidly decided to remove and no addon does the same job as well.

Mozilla just sucks, to be frank. They can't seem to have any coherent idea about what Firefox should be. The big redesign alienated a lot of the people who used it for its customisation. Adding in unwanted features like Pocket integration made people doubt the credibility of Mozilla's claims of privacy. And cockups like everyones' addons stopping working, despite being warned by the community it would happen, leave a bitter taste in peoples' mouths.