It wuz Russians. No investigation needed. /sarc
I suspect that the investigation folks have a fairly good idea about who did it, and the ‘shoe’ will fall in the middle of this campaign period...likely leading to Green Party or Linke Party official within the Bundestag.
If you look at polling right now....the Greens are down to the lowest point of the past twenty years. If this connects back to one of their group...you might see them get less than 5-percent of the national vote in September, and thus not sit in the Bundestag for the next four years.