Wagenknecht will not lead to a strong left in Germany. The people that voted left before voted left because Gysi and the reasonable opinions he portrayed. Wagenknecht is only a magnet for extremists, that would vote far right (AfD) if it wasn’t for the blatant racism/antisemitism/etc.
If anything the the leftist party will gain more mainstream approval, when Wagenknecht forks off her own party (except for east Germany).