It's pragmatic to leave Chrome for the exact same reasons people left IE, the parent company has stopped improving the product.

Chrome sold people on the promise of a much faster, lighter-weight browser than the heavy but competent Firefox of the time, a promise that Chrome no longer delivers on. The "added users" Mozilla has claimed in 2016 were developers realizing Chrome wasn't light or speedy anymore and if they were going to use a browser hogging all the RAM on their system they may as well use one with a functional extensions ecosystem.

Chrome may not be comparatively "as bad" as IE was at the peak of Firefox's success, but it's still suffering from the same disease.