I feel like saying 2048 "ripped off" Threes is like saying Celeste ripped off Super Meat Boy. There's absolutely an inspirational connection between, but the games appeal to different people. Threes is less popular because it's drastically harder.
Threes made the fatal mistake of charging money on the App Store.
The bigger mistake was being single-platform.
I think the fact that 2048 was first released on GitHub pages was one of the reasons for its success. Virtually limitless resource for free.