TFM worldwide. Way more global hits (Just Dance, Poker Face, Bad Romance, Telephone while 1989 only had Shake It Off and Blank Space) and more global album sales
1989 was bigger in US, Canada, and Australia only, it didn't even do that well anywhere else
The Fame Monster. We saw the rise and complete dominance of one Pop star in a landscape saturated with already big names.
Taylor had no competition for 1989 from any of the veterans. Just the up and coming Disney stars. It was much easier for Taylaor to "feel" bigger and "dominate" more with 1989.