It's well worth reading the Spiegel piece from a year ago, which is far more in-depth and goes over a lot more of the evidence and plausibility of the scenario. It's odd to me ARD would put out this highly similar but 90% slimmed down and far less convincing article and not even mention the earlier and more authoritative Spiegel report.
https://www.spiegel.de/international/europe/investigating-th...