Not sure what you mean, the center parties are still the strongest. Not everything follows this caricature of left/right that seems to be so prevalent online these days.
Discussion
It is rather clear from the outside that the policies in Germany are not centrist at all, but rather, quite leftist.
This easily explains why the "far" right is gaining momentum, things skewed left so hard for so long, equilibrium is trying to reassert itself.
It’s more so been center-left. Interestingly, the far left party also almost doubled their results (to 8.8%).
I suppose that depends on what you consider the center to be. But that is almost entirely subjective of course.
For my sensibilities (and I have visited many times and have many German friends) it doesn't feel centrish at all, but evidently for you it does, it is what it is, difference of opinion/perspective.