I don't know if "being better than Trump" should necessarily be the bar we set for "greatness".
The political spectrum skews further to the left in all of the countries listed in the article on a number of social issues:
Canada, Belgium, France, Germany, Greece, Italy, the Netherlands, Spain, Sweden, the UK, Australia, Japan, New Zealand, Singapore, South Korea and Taiwan.
Basically, anyone who's left of center in the US is going to be more popular in those areas than anyone who's right of center. Combined with the fact that Trump was exceptionally bad and abrasive (and the rebound effect makes even a mediocre person seem great if their predecessor was terrible), I'm not surprised that the numbers are what they are.
To use an inverse example...
If you can remember all the way back to the early-mid 90's... Boris Yeltsin was someone who many in the international community liked (or at least pretended to) He and Bill Clinton got along well. Yeltsin wasn't a great leader, in fact he had a lot of issues and some concerning policies, but he won some favor simply by not being Gorbachev, Chernenko, or Brezhnev, and being better than his predecessors. (as the 3 aforementioned Russian leaders had some seriously bad PR attached to them due the the Eastern Bloc/Cold War situation)