Having sustained success, Ronaldo left for Germany, surprisingly (2,1,4)
I believe the answer is:
on a roll
I'm afraid I can't explain this answer.
Can you help me to learn more?
(Other definitions for on a roll that I've seen before include "continually successful" , "Enjoying a winning streak" , "Going through a good patch" , "Hitting a purple patch (as bacon might be?)" , "enjoying lots of success" .)