Barca constantly have got the better of Real and Messi has been very good last two times against them. All time great in one.
Messi also does it againsy Atletico.
So it is not about destroying weak teams.
Nothing to do with being fickle. It is completely fair to expect more from Messi than today.
Why is Messi able to perform in La Liga?
You're acting like Messi hasn't performed in the Champions League. His goalscoring speaks for itself in the Champions League. He cannot put in a goat performance all the time, especially with that Barcelona team. He still needs support! Why can't you get that into your head?